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Dancer - lightweight yet powerful web application framework


version 1.3521


    use Dancer;

    get '/hello/:name' => sub {
        return "Why, hello there " . param('name');


The above is a basic but functional web app created with Dancer. If you want to see more examples and get up and running quickly, check out the Dancer::Introduction and the Dancer::Cookbook. For examples on deploying your Dancer applications, see Dancer::Deployment.


Dancer is a web application framework designed to be as effortless as possible for the developer, taking care of the boring bits as easily as possible, yet staying out of your way and letting you get on with writing your code.

Dancer aims to provide the simplest way for writing web applications, and offers the flexibility to scale between a very simple lightweight web service consisting of a few lines of code in a single file, all the way up to a more complex fully-fledged web application with session support, templates for views and layouts, etc.

If you don't want to write CGI scripts by hand, and find Catalyst too big or cumbersome for your project, Dancer is what you need.

Dancer has few pre-requisites, so your Dancer webapps will be easy to deploy.

Dancer apps can be used with an embedded web server (great for easy testing), and can run under PSGI/Plack for easy deployment in a variety of webserver environments.


This documentation describes all the exported symbols of Dancer. If you want a quick start guide to discover the framework, you should look at Dancer::Introduction, or Dancer::Tutorial to learn by example.

If you want to have specific examples of code for real-life problems, see the Dancer::Cookbook.

If you want to see configuration examples of different deployment solutions involving Dancer and Plack, see Dancer::Deployment.

You can find out more about the many useful plugins available for Dancer in Dancer::Plugins.


This is the original version of Dancer, which is now in maintenance mode. This means that it will not receive significant new features, but will continue to receive bugfixes and security fixes. However, no "end of life" date has been set, and it is expected that this version of Dancer will continue to receive bugfixes and security fixes for quite some time yet.

However, you should consider migrating to Dancer2 instead when you can, and are advised to use Dancer2 for newly-started apps.

Dancer2 is mostly backwards compatible, but has been re-written from the ground up to be more maintainable and extensible, and is the future of Dancer.

Dancer2::Manual::Migration covers the changes you should be aware of when migrating an existing Dancer 1 powered app to Dancer 2.


By default, use Dancer exports all the functions below plus sets up your app. You can control the exporting through the normal Exporter mechanism. For example:

    # Just export the route controllers
    use Dancer qw(get post put patch del);

    # Export everything but pass to avoid clashing with Test::More
    use Test::More;
    use Dancer qw(!pass);

Please note that the utf8 and strict pragmas are exported by this module.

By default, the warnings pragma will also be exported, meaning your app/script will be running under use warnings. If you do not want this, set the global_warnings setting to a false value.

There are also some special tags to control exports and behaviour.


This will export everything except functions which clash with Moose. Currently these are after and before.


This tells Dancer to just export symbols and not set up your app. This is most useful for writing Dancer code outside of your main route handler.


This will export everything except functions which clash with commonly used testing modules. Currently these are pass.

It can be combined with other export pragmas. For example, while testing...

    use Test::More;
    use Dancer qw(:syntax :tests);

    # Test::Most also exports "set" and "any"
    use Test::Most;
    use Dancer qw(:syntax :tests !set !any);

    # Alternatively, if you want to use Dancer's set and any...
    use Test::Most qw(!set !any);
    use Dancer qw(:syntax :tests);


This will export all the keywords, load the configuration, and will not try to parse command-line arguments via Dancer::GetOpt.

This is useful when you want to use your Dancer application from a script.

    use MyApp;
    use Dancer ':script';

Note that using :script will disable command-line parsing for all subsequent invocations of use Dancer (such that you don't have to use :script for each and every module to make sure the command-line arguments don't get stolen by Dancer).


If you want to simply prevent Dancer from exporting specific keywords (perhaps you plan to implement them yourself in a different way, or you don't plan to use them and they clash with another module you're loading), you can simply exclude them:

    use Dancer qw(!session);

The above would import all keywords as normal, with the exception of session.



Deprecated - see the after hook.


Defines a route for multiple HTTP methods at once:

    any ['get', 'post'] => '/myaction' => sub {
        # code

Or even, a route handler that would match any HTTP methods:

    any '/myaction' => sub {
        # code


Deprecated - see the before hook.


Deprecated - see the before_template hook.


Accesses cookies values, it returns a HashRef of Dancer::Cookie objects:

    get '/some_action' => sub {
        my $cookie = cookies->{name};
        return $cookie->value;

In the case you have stored something other than a Scalar in your cookie:

    get '/some_action' => sub {
        my $cookie = cookies->{oauth};
        my %values = $cookie->value;
        return ($values{token}, $values{token_secret});

Accesses a cookie value (or sets it). Note that this method will eventually be preferred over set_cookie.

    cookie lang => "fr-FR";              # set a cookie and return its value
    cookie lang => "fr-FR", expires => "2 hours";   # extra cookie info
    cookie "lang"                        # return a cookie value

If your cookie value is a key/value URI string, like


cookie will only return the first part (token=ABC) if called in scalar context. Use list context to fetch them all:

    my @values = cookie "name";

Note that if the client has sent more than one cookie with the same value, the one returned will be the last one seen. This should only happen if you have set multiple cookies with the same name but different paths. So, don't do that.


Accesses the configuration of the application:

    get '/appname' => sub {
        return "This is " . config->{appname};


Sets the content-type rendered, for the current route handler:

    get '/cat/:txtfile' => sub {
        content_type 'text/plain';

        # here we can dump the contents of param('txtfile')

You can use abbreviations for content types. For instance:

    get '/svg/:id' => sub {
        content_type 'svg';

        # here we can dump the image with id param('id')

Note that if you want to change the default content-type for every route, you have to change the content_type setting instead.


Alias for the start keyword.


Returns the version of Dancer. If you need the major version, do something like:



Logs a message of debug level:

    debug "This is a debug message";

See Dancer::Logger for details on how to configure where log messages go.


Returns the dirname of the path given:

    my $dir = dirname($some_path);


Given a namespace, returns the current engine object

    my $template_engine = engine 'template';
    my $html = $template_engine->apply_renderer(...);


Logs a message of error level:

    error "This is an error message";

See Dancer::Logger for details on how to configure where log messages go.


Constant that returns a false value (0).


Runs an internal redirect of the current request to another request. This helps you avoid having to redirect the user using HTTP and set another request to your application.

It effectively lets you chain routes together in a clean manner.

    get '/demo/articles/:article_id' => sub {

        # you'll have to implement this next sub yourself :)

        forward "/articles/" . params->{article_id};

In the above example, the users that reach /demo/articles/30 will actually reach /articles/30 but we've changed the database to demo before.

This is pretty cool because it lets us retain our paths and offer a demo database by merely going to /demo/....

You'll notice that in the example we didn't indicate whether it was GET or POST. That is because forward chains the same type of route the user reached. If it was a GET, it will remain a GET (but if you do need to change the method, you can do so; read on below for details.)

WARNING : using forward will not preserve session data set on the forwarding rule.

WARNING : Issuing a forward immediately exits the current route, and perform the forward. Thus, any code after a forward is ignored, until the end of the route. e.g.

    get '/foo/:article_id' => sub {
        if ($condition) {
            forward "/articles/" . params->{article_id};
            # The following code is never executed


So it's not necessary anymore to use return with forward.

Note that forward doesn't parse GET arguments. So, you can't use something like:

     return forward '/home?authorized=1';

But forward supports an optional HashRef with parameters to be added to the actual parameters:

     return forward '/home', { authorized => 1 };

Finally, you can add some more options to the forward method, in a third argument, also as a HashRef. That option is currently only used to change the method of your request. Use with caution.

    return forward '/home', { auth => 1 }, { method => 'POST' };

from_dumper ($structure)

Deserializes a Data::Dumper structure.

from_json ($structure, \%options)

Deserializes a JSON structure. Can receive optional arguments. Those arguments are valid JSON arguments to change the behaviour of the default JSON::from_json function.

Compatibility notice: from_json changed in 1.3002 to take a hashref as options, instead of a hash.

from_yaml ($structure)

Deserializes a YAML structure.

from_xml ($structure, %options)

Deserializes a XML structure. Can receive optional arguments. These arguments are valid XML::Simple arguments to change the behaviour of the default XML::Simple::XMLin function.


Defines a route for HTTP GET requests to the given path:

    get '/' => sub {
        return "Hello world";

Note that a route to match HEAD requests is automatically created as well.


Sets a response object with the content given.

When used as a return value from a filter, this breaks the execution flow and renders the response immediately:

    hook before sub {
        if ($some_condition) {
            # This code is not executed :

    get '/' => sub {
        "hello there";

WARNING : Issuing a halt immediately exits the current route, and perform the halt. Thus, any code after a halt is ignored, until the end of the route. So it's not necessary anymore to use return with halt.


Adds custom headers to responses:

    get '/send/headers', sub {
        headers 'X-Foo' => 'bar', X-Bar => 'foo';

adds a custom header to response:

    get '/send/header', sub {
        header 'x-my-header' => 'shazam!';

Note that it will overwrite the old value of the header, if any. To avoid that, see "push_header".


Do the same as header, but allow for multiple headers with the same name.

    get '/send/header', sub {
        push_header 'x-my-header' => '1';
        push_header 'x-my-header' => '2';
        will result in two headers "x-my-header" in the response


Adds a hook at some position. For example :

  hook before_serializer => sub {
    my $response = shift;
    $response->content->{generated_at} = localtime();

There can be multiple hooks assigned to a given position, and each will be executed in order. Note that all hooks are always called, even if they are defined in a different package loaded via load_app.

(For details on how to register new hooks from within plugins, see Dancer::Hook.) Supported before hooks (in order of execution):


This hook receives no arguments.

  hook before_deserializer => sub {

This hook receives as argument the path of the file to render.

  hook before_file_render => sub {
    my $path = shift;

This hook receives as argument a Dancer::Error object.

  hook before_error_init => sub {
    my $error = shift;

This hook receives as argument a Dancer::Error object.

  hook before_error_render => sub {
    my $error = shift;

This hook receives one argument, the route being executed (a Dancer::Route object).

  hook before => sub {
    my $route_handler = shift;

it is equivalent to the deprecated

  before sub {

This is an alias to 'before_template'.

This hook receives as argument a HashRef containing the tokens that will be passed to the template. You can use it to add more tokens, or delete some specific token.

  hook before_template_render => sub {
    my $tokens = shift;
    delete $tokens->{user};
    $tokens->{time} = localtime;

is equivalent to

  hook before_template => sub {
    my $tokens = shift;
    delete $tokens->{user};
    $tokens->{time} = localtime;

This hook receives two arguments. The first one is a HashRef containing the tokens. The second is a ScalarRef representing the content of the template.

  hook before_layout_render => sub {
    my ($tokens, $html_ref) = @_;

This hook receives as argument a Dancer::Response object.

  hook before_serializer => sub {
    my $response = shift;
    $response->content->{start_time} = time();

Supported after hooks (in order of execution):


This hook receives no arguments.

  hook after_deserializer => sub {

This hook receives as argument a Dancer::Response object.

  hook after_file_render => sub {
    my $response = shift;

This hook receives as argument a ScalarRef representing the content generated by the template.

  hook after_template_render => sub {
    my $html_ref = shift;

This hook receives as argument a ScalarRef representing the content generated by the layout

  hook after_layout_render => sub {
    my $html_ref = shift;

This is an alias for after.

This hook runs after a request has been processed, but before the response is sent.

It receives a Dancer::Response object, which it can modify if it needs to make changes to the response which is about to be sent.

  hook after => sub {
    my $response = shift;

This is equivalent to the deprecated

  after sub {
    my $response = shift;

This hook receives as argument a Dancer::Response object.

  hook after_error_render => sub {
    my $response = shift;

This hook is called when an exception has been caught, at the handler level, just before creating and rendering Dancer::Error. This hook receives as argument a Dancer::Exception object.

  hook on_handler_exception => sub {
    my $exception = shift;

This hook is called when global state is reset to process a new request. It receives a boolean value that indicates whether the reset was called as part of a forwarded request.

  hook on_reset_state => sub {
    my $is_forward = shift;

This hook is called when an exception has been caught, at the route level, just before rethrowing it higher. This hook receives the exception as argument. It can be a Dancer::Exception, or a string, or whatever was used to die.

  hook on_route_exception => sub {
    my $exception = shift;


Logs a message of info level:

    info "This is a info message";

See Dancer::Logger for details on how to configure where log messages go.


This method is deprecated. Use set:

    set layout => 'user';


Deprecated. Use <set logger => 'console'> to change current logger engine.


Loads one or more perl scripts in the current application's namespace. Syntactic sugar around Perl's require:

    load '', '';


Loads a Dancer package. This method sets the libdir to the current ./lib directory:

    # if we have lib/, we can load it like:
    load_app 'Webapp';
    # or with options
    load_app 'Forum', prefix => '/forum', settings => {foo => 'bar'};

Note that the package loaded using load_app must import Dancer with the :syntax option.

To load multiple apps repeat load_app:

    load_app 'one';
    load_app 'two';

The old way of loading multiple apps in one go (load_app 'one', 'two';) is deprecated.


Shortcut to access the instance object of Dancer::MIME. You should read the Dancer::MIME documentation for full details, but the most commonly-used methods are summarized below:

    # set a new mime type
    mime->add_type( foo => 'text/foo' );

    # set a mime type alias
    mime->add_alias( f => 'foo' );

    # get mime type for an alias
    my $m = mime->for_name( 'f' );

    # get mime type for a file (based on extension)
    my $m = mime->for_file( "" );

    # get current defined default mime type
    my $d = mime->default;

    # set the default mime type using config.yml
    # or using the set keyword
    set default_mime_type => 'text/plain';


This method should be called from a route handler. It's an alias for the Dancer::Request params accessor. In list context it returns a list of key/value pair of all defined parameters. In scalar context it returns a hash reference instead. Check param below to access quickly to a single parameter value.


This method should be called from a route handler. This method is an accessor to the parameters hash table.

   post '/login' => sub {
       my $username = param "user";
       my $password = param "pass";
       # ...


This method should be called from a route handler. Like param, but always returns the parameter value or values as a list. Returns the number of values in scalar context.

    # if request is '/tickets?tag=open&tag=closed&order=desc'...
    get '/tickets' => sub {
        my @tags = param_array 'tag';  # ( 'open', 'closed' )
        my $tags = param 'tag';        # array ref

        my @order = param_array 'order';  # ( 'desc' )
        my $order = param 'order';        # 'desc'


This method should be called from a route handler. Tells Dancer to pass the processing of the request to the next matching route.

WARNING : Issuing a pass immediately exits the current route, and performs the pass. Thus, any code after a pass is ignored until the end of the route. So it's not necessary any more to use return with pass.

    get '/some/route' => sub {
        if (...) {
            # we want to let the next matching route handler process this one
            # This code will be ignored


Defines a route for HTTP PATCH requests to the given URL:

    patch '/resource' => sub { ... };

(PATCH is a relatively new and not-yet-common HTTP verb, which is intended to work as a "partial-PUT", transferring just the changes; please see|RFC5789 for further details.)

Please be aware that, if you run your app in standalone mode, PATCH requests will not reach your app unless you have a new version of HTTP::Server::Simple which accepts PATCH as a valid verb. The current version at time of writing, 0.44, does not. A pull request has been submitted to add this support, which you can find at:


Concatenates multiple paths together, without worrying about the underlying operating system:

    my $path = path(dirname($0), 'lib', '');

It also normalizes (cleans) the path aesthetically. It does not verify the path exists.


Defines a route for HTTP POST requests to the given URL:

    post '/' => sub {
        return "Hello world";


Defines a prefix for each route handler, like this:

    prefix '/home';

From here, any route handler is defined to /home/*:

    get '/page1' => sub {}; # will match '/home/page1'

You can unset the prefix value:

    prefix undef;
    get '/page1' => sub {}; will match /page1

For a safer alternative you can use lexical prefix like this:

    prefix '/home' => sub {
        ## Prefix is set to '/home' here

        get ...;
        get ...;
    ## prefix reset to the previous version here

This makes it possible to nest prefixes:

   prefix '/home' => sub {
       ## some routes
      prefix '/private' => sub {
         ## here we are under /home/private...

         ## some more routes
      ## back to /home
   ## back to the root

Notice: once you have a prefix set, do not add a caret to the regex:

    prefix '/foo';
    get qr{^/bar} => sub { ... } # BAD BAD BAD
    get qr{/bar}  => sub { ... } # Good!


Defines a route for HTTP DELETE requests to the given URL:

    del '/resource' => sub { ... };


Defines a route for HTTP OPTIONS requests to the given URL:

    options '/resource' => sub { ... };


Defines a route for HTTP PUT requests to the given URL:

    put '/resource' => sub { ... };


Generates an HTTP redirect (302). You can either redirect to a completely different site or within the application:

    get '/twitter', sub {
        redirect '';

You can also force Dancer to return a specific 300-ish HTTP response code:

    get '/old/:resource', sub {
        redirect '/new/'.params->{resource}, 301;

It is important to note that issuing a redirect by itself does not exit and redirect immediately. Redirection is deferred until after the current route or filter has been processed. To exit and redirect immediately, use the return function, e.g.

    get '/restricted', sub {
        return redirect '/login' if accessDenied();
        return 'Welcome to the restricted section';


Allows a handler to provide plain HTML (or other content), but have it rendered within the layout still.

This method is DEPRECATED, and will be removed soon. Instead, you should be using the engine keyword:

    get '/foo' => sub {
        # Do something which generates HTML directly (maybe using
        # HTML::Table::FromDatabase or something)
        my $content = ...;

        # get the template engine
        my $template_engine = engine 'template';

        # apply the layout (not the renderer), and return the result

It works very similarly to template in that you can pass tokens to be used in the layout, and/or options to control the way the layout is rendered. For instance, to use a custom layout:

    render_with_layout $content, {}, { layout => 'layoutname' };


Returns a Dancer::Request object representing the current request.

See the Dancer::Request documentation for the methods you can call, for example:

    request->referer;         # value of the HTTP referer header
    request->remote_address;  # user's IP address
    request->user_agent;      # User-Agent header value


Returns an HTTP error. By default the HTTP code returned is 500:

    get '/photo/:id' => sub {
        if (...) {
            send_error("Not allowed", 403);
        } else {
           # return content

WARNING : Issuing a send_error immediately exits the current route, and perform the send_error. Thus, any code after a send_error is ignored, until the end of the route. So it's not necessary anymore to use return with send_error.

    get '/some/route' => sub {
        if (...) {
            # we want to let the next matching route handler process this one
            # This code will be ignored


Lets the current route handler send a file to the client. Note that the path of the file must be relative to the public directory unless you use the system_path option (see below).

    get '/download/:file' => sub {

WARNING : Issuing a send_file immediately exits the current route, and performs the send_file. Thus, any code after a send_file is ignored until the end of the route. So it's not necessary any more to use return with send_file.

    get '/some/route' => sub {
        if (...) {
            # we want to let the next matching route handler process this one
            # This code will be ignored

Send file supports streaming possibility using PSGI streaming. The server should support it but normal streaming is supported on most, if not all.

    get '/download/:file' => sub {
        send_file( params->{file}, streaming => 1 );

You can control what happens using callbacks.

First, around_content allows you to get the writer object and the chunk of content read, and then decide what to do with each chunk:

    get '/download/:file' => sub {
            streaming => 1,
            callbacks => {
                around_content => sub {
                    my ( $writer, $chunk ) = @_;
                    $writer->write("* $chunk");

You can use around to all get all the content (whether a filehandle if it's a regular file or a full string if it's a scalar ref) and decide what to do with it:

    get '/download/:file' => sub {
            streaming => 1,
            callbacks => {
                around => sub {
                    my ( $writer, $content ) = @_;

                    # we know it's a text file, so we'll just stream
                    # line by line
                    while ( my $line = <$content> ) {

Or you could use override to control the entire streaming callback request:

    get '/download/:file' => sub {
            streaming => 1,
            callbacks => {
                override => sub {
                    my ( $respond, $response ) = @_;

                    my $writer = $respond->( [ $newstatus, $newheaders ] );
                    $writer->write("some line");

You can also set the number of bytes that will be read at a time (default being 42K bytes) using bytes:

    get '/download/:file' => sub {
            streaming => 1,
            bytes     => 524288, # 512K

The content-type will be set depending on the current MIME types definition (see mime if you want to define your own).

If your filename does not have an extension, or you need to force a specific mime type, you can pass it to send_file as follows:

    send_file(params->{file}, content_type => 'image/png');

Also, you can use your aliases or file extension names on content_type, like this:

    send_file(params->{file}, content_type => 'png');

For files outside your public folder, you can use the system_path switch. Just bear in mind that its use needs caution as it can be dangerous.

   send_file('/etc/passwd', system_path => 1);

If you have your data in a scalar variable, send_file can be useful as well. Pass a reference to that scalar, and send_file will behave as if there were a file with that contents:

   send_file( \$data, content_type => 'image/png' );

Note that Dancer is unable to guess the content type from the data contents. Therefore you might need to set the content_type properly. For this kind of usage an attribute named filename can be useful. It is used as the Content-Disposition header, to hint the browser about the filename it should use.

   send_file( \$data, content_type => 'image/png'
                             filename     => 'onion.png' );


Defines a setting:

    set something => 'value';

You can set more than one value at once:

    set something => 'value', otherthing => 'othervalue';


Returns the value of a given setting:

    setting('something'); # 'value'

Creates or updates cookie values:

    get '/some_action' => sub {
        set_cookie name => 'value',
                   expires => (time + 3600),
                   domain  => '';

In the example above, only 'name' and 'value' are mandatory.

You can also store more complex structure in your cookies:

    get '/some_auth' => sub {
        set_cookie oauth => {
            token        => $twitter->request_token,
            token_secret => $twitter->secret_token,

You can't store more complex structure than this. All keys in the HashRef should be Scalars; storing references will not work.

See Dancer::Cookie for further options when creating your cookie.

Note that this method will be eventually deprecated in favor of the new cookie method.


Provides access to all data stored in the user's session (if any).

It can also be used as a setter to store data in the session:

    # getter example
    get '/user' => sub {
        if (session('user')) {
            return "Hello, ".session('user')->name;

    # setter example
    post '/user/login' => sub {
        if ($logged_in) {
            session user => $user;

You may also need to clear a session:

    # destroy session
    get '/logout' => sub {

If you need to fetch the session ID being used for any reason:

    my $id = session->id;

In order to be able to use sessions, first you need to enable session support in one of the configuration files. A quick way to do it is to add

    session: "YAML"

to config.yml.

For more details, see Dancer::Session.


Returns the list of captures made from a route handler with a route pattern which includes wildcards:

    get '/file/*.*' => sub {
        my ($file, $extension) = splat;

There is also the extensive splat (A.K.A. "megasplat"), which allows extensive greedier matching, available using two asterisks. The additional path is broken down and returned as an ArrayRef:

    get '/entry/*/tags/**' => sub {
        my ( $entry_id, $tags ) = splat;
        my @tags = @{$tags};

This helps with chained actions:

    get '/team/*/**' => sub {
        my ($team) = splat;
        var team => $team;

    prefix '/team/*';

    get '/player/*' => sub {
        my ($player) = splat;

        # etc...

    get '/score' => sub {
        return score_for( vars->{'team'} );


Starts the application or the standalone server (depending on the deployment choices).

This keyword should be called at the very end of the script, once all routes are defined. At this point, Dancer takes over control.


Changes the status code provided by an action. By default, an action will produce an HTTP 200 OK status code, meaning everything is OK:

    get '/download/:file' => {
        if (! -f params->{file}) {
            status 'not_found';
            return "File does not exist, unable to download";
        # serving the file...

In that example Dancer will notice that the status has changed, and will render the response accordingly.

The status keyword receives either a numeric status code or its name in lower case, with underscores as a separator for blanks. See the list in "HTTP CODES" in Dancer::HTTP.


Returns the response of processing the given template with the given parameters (and optional settings), wrapping it in the default or specified layout too, if layouts are in use.

An example of a route handler which returns the result of using template to build a response with the current template engine:

    get '/' => sub {
        return template 'some_view', { token => 'value'};

Note that template simply returns the content, so when you use it in a route handler, if execution of the route handler should stop at that point, make sure you use 'return' to ensure your route handler returns the content.

Since template just returns the result of rendering the template, you can also use it to perform other templating tasks, e.g. generating emails:

    post '/some/route' => sub {
        if (...) {
            email {
                to      => '',
                from    => '',
                subject => 'Hello there',
                msg     => template('emails/foo', { name => params->{name} }),

            return template 'message_sent';
        } else {
            return template 'error';

Compatibility notice: template was changed in version 1.3090 to immediately interrupt execution of a route handler and return the content, as it's typically used at the end of a route handler to return content. However, this caused issues for some people who were using template to generate emails etc, rather than accessing the template engine directly, so this change has been reverted in 1.3091.

The first parameter should be a template available in the views directory, the second one (optional) is a HashRef of tokens to interpolate, and the third (again optional) is a HashRef of options.

For example, to disable the layout for a specific request:

    get '/' => sub {
        template 'index', {}, { layout => undef };

Or to request a specific layout, of course:

    get '/user' => sub {
        template 'user', {}, { layout => 'user' };

Some tokens are automatically added to your template (perl_version, dancer_version, settings, request, params, vars and, if you have sessions enabled, session). Check Dancer::Template::Abstract for further details.

to_dumper ($structure)

Serializes a structure with Data::Dumper.

to_json ($structure, \%options)

Serializes a structure to JSON. Can receive optional arguments. Thoses arguments are valid JSON arguments to change the behaviour of the default JSON::to_json function.

Compatibility notice: to_json changed in 1.3002 to take a hashref as options, instead of a hash.

to_yaml ($structure)

Serializes a structure to YAML.

to_xml ($structure, %options)

Serializes a structure to XML. Can receive optional arguments. Thoses arguments are valid XML::Simple arguments to change the behaviour of the default XML::Simple::XMLout function.


Constant that returns a true value (1).


Provides access to file uploads. Any uploaded file is accessible as a Dancer::Request::Upload object. You can access all parsed uploads via:

    post '/some/route' => sub {
        my $file = upload('file_input_foo');
        # file is a Dancer::Request::Upload object

If you named multiple inputs of type "file" with the same name, the upload keyword will return an Array of Dancer::Request::Upload objects:

    post '/some/route' => sub {
        my ($file1, $file2) = upload('files_input');
        # $file1 and $file2 are Dancer::Request::Upload objects

You can also access the raw HashRef of parsed uploads via the current request object:

    post '/some/route' => sub {
        my $all_uploads = request->uploads;
        # $all_uploads->{'file_input_foo'} is a Dancer::Request::Upload object
        # $all_uploads->{'files_input'} is an ArrayRef of Dancer::Request::Upload objects

Note that you can also access the filename of the upload received via the params keyword:

    post '/some/route' => sub {
        # params->{'files_input'} is the filename of the file uploaded

See Dancer::Request::Upload for details about the interface provided.


Returns a fully-qualified URI for the given path:

    get '/' => sub {
        redirect uri_for('/path');
        # can be something like: http://localhost:3000/path

Querystring parameters can be provided by passing a hashref as a second param, and URL-encoding can be disabled via a third parameter:

    uri_for('/path', { foo => 'bar' }, 1);
    # would return e.g. http://localhost:3000/path?foo=bar


Returns a reference to a copy of %+, if there are named captures in the route Regexp.

Named captures are a feature of Perl 5.10, and are not supported in earlier versions:

    get qr{
        / (?<object> user   | ticket | comment )
        / (?<action> delete | find )
        / (?<id> \d+ )
    , sub {
        my $value_for = captures;
        "i don't want to $$value_for{action} the $$value_for{object} $$value_for{id} !"


Provides an accessor for variables shared between filters and route handlers. Given a key/value pair, it sets a variable:

    hook before sub {
        var foo => 42;

Later, route handlers and other filters will be able to read that variable:

    get '/path' => sub {
        my $foo = var 'foo';


Returns the HashRef of all shared variables set during the filter/route chain with the var keyword:

    get '/path' => sub {
        if (vars->{foo} eq 42) {


Logs a warning message through the current logger engine:

    warning "This is a warning";

See Dancer::Logger for details on how to configure where log messages go.


This module has been written by Alexis Sukrieh <> and others, see the AUTHORS file that comes with this distribution for details.


The source code for this module is hosted on GitHub Feel free to fork the repository and submit pull requests! (See Dancer::Development for details on how to contribute).

Also, why not watch the repo to keep up to date with the latest upcoming changes?


The Dancer development team can be found on #dancer on irc://

If you don't have an IRC client installed/configured, there is a simple web chat client at for you.

There is also a Dancer users mailing list available. Subscribe at:

If you'd like to contribute to the Dancer project, please see for all the ways you can help!


The following modules are mandatory (Dancer cannot run without them):


The following modules are optional:

JSON : needed to use JSON serializer
Plack : in order to use PSGI
Template : in order to use TT for rendering views
XML::Simple and XML:SAX or XML:Parser for XML serialization
YAML : needed for configuration file support


Main Dancer web site:

The concept behind this module comes from the Sinatra ruby project, see for details.


Dancer Core Developers


This software is copyright (c) 2010 by Alexis Sukrieh.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.