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40 non-PAUSE users
Author image Ferenc Erki
and 118 contributors


Rex::Template - simple template engine


 use Rex::Template;

 my $template = Rex::Template->new;

 print $template->parse($content, \%template_vars);
 print $template->parse($content, @template_vars);


This is a simple template engine for configuration files. It is included mostly for backwards compatibility, and it is recommended to use Rex::Template::NG instead (for better control of chomping new lines, and better diagnostics if things go wrong).


The following syntax is recognized:

  • anything between <% and %> markers are considered as a template directive, which is treated as Perl code

  • if the opening marker is followed by an equal sign (<%=) or a plus sign (<%+), then the directive is replaced with the value it evaluates to

  • if the closing marker is prefixed with a minus sign (-%>), then any trailing newlines are chomped for that directive

The built-in template support is intentionally kept basic and simple. For anything more sophisticated, please use your favorite template engine.


Plain text is unchanged:

 my $result = $template->parse( 'one two three', {} );

 # $result is 'one two three'

Variable interpolation:

 my $result = template->parse( 'Hello, this is <%= $::name %>', { name => 'foo' } ); # original format
 my $result = template->parse( 'Hello, this is <%+ $::name %>', { name => 'foo' } ); # alternative format with + sign
 my $result = template->parse( 'Hello, this is <%= $name %>',   { name => 'foo' } ); # local variables
 my $result = template->parse( 'Hello, this is <%= $name %>',     name => 'foo'   ); # array of variables, instead of hashref

 # $result is 'Hello, this is foo' for all cases above

Simple evaluation:

 my $result = $template->parse( '<%= join("/", @{$elements} ) %>', elements => [qw(one two three)] );
 # $result is 'one/two/three'

Embedded code blocks:

 my $content = '<% if ($logged_in) { %>
 Logged in!
 <% } else { %>
 Logged out!
 <% } %>';

 my $result = $template->parse( $content, logged_in => 1 );

 # $result is "\nLogged in!\n"


Not much, mainly due to the internal approach of the module.

If there was a problem, it prints an INFO level "syntax error at ...", followed by a WARN about "It seems that there was an error processing the template because the result is empty.", and finally "Error processing template at ...".

The beginning of the reported syntax error might give some clue where the error happened in the template, but that's it.

Use Rex::Template::NG instead for better diagnostics.


If $Rex::Template::BE_LOCAL is set to a true value, then local template variables are supported instead of only global ones ($foo vs $::foo). The default value is 1 since Rex-0.41. It can be disabled with the no_local_template_vars feature flag.

If $Rex::Template::DO_CHOMP is set to a true value, then any trailing new line character resulting from template directives are chomped. Defaults to 0.

This module does not support any environment variables.


parse($content, $variables)

Parse $content as a template, using $variables hash reference to pass name-value pairs of variables to make them available for the template function.

Alternatively, the variables may be passed as an array instead of a hash reference.

is_defined($variable, $default_value)

This function will check if $variable is defined. If yes, it will return the value of $variable, otherwise it will return $default_value.

You can use this function inside your templates, for example:

 ServerTokens <%= is_defined( $::server_tokens, 'Prod' ) %>




It might not be able to chomp new line characters resulting from templates in every case.

It can't report useful diagnostic messages upon errors.

Use Rex::Template::NG instead.