Devel::Examine::Subs - Get info about, search/replace and inject code into Perl files and subs.

Coverage Status


Gather information about subroutines in Perl files (and in-memory modules), with the ability to search/replace code, inject new code, get line counts, get start and end line numbers, access the sub's code and a myriad of other options. Files are parsed using PPI, not by inspecting packages or coderefs.


    use Devel::Examine::Subs;

    # examine a file

    my $des = Devel::Examine::Subs->new( file => '' );

    # examine all the Perl files in a directory

    my $des = Devel::Examine::Subs->new( file => '/path/to/directory' );

    # load a module by name. Uses %INC to find the path after loading it

    my $des = Devel::Examine::Subs->new( file => 'Some::Module::Name' );

Get all sub names in a file

    my $aref = $des->all;

Get all the subs as objects

    $subs = $des->objects;

    for my $sub (@$subs){
        $sub->name;       # name of sub
        $sub->start;      # first line number of sub in file
        $sub->end;        # last line number of sub in file
        $sub->line_count; # number of lines in sub
        $sub->code;       # entire sub code from file
        $sub->lines;      # lines that match search term

Get the sub objects within a hash

    my $subs = $des->objects( objects_in_hash => 1 );

    for my $sub_name (keys %$subs) {

        print "$sub_name\n";

        my $sub = $subs->{$sub_name};

        print $sub->start . "\n" .
              $sub->end . "\n";

Get all subs containing "string" in the body

    my $search = 'string';
    my $aref = $des->has( search => $search );

Search and replace code in subs

    $des->search_replace( exec => sub { $_[0] =~ s/this/that/g; } );

Inject code into sub after a search term (preserves previous line's indenting)

    my @code = <DATA>;

                    search => 'this',
                    code => \@code,


    # previously uncaught issue

    if ($foo eq "bar"){
        confess 'big bad error';

Print out all lines in all subs that contain a search term

    my $subs = $des->lines(search => 'this');

    for my $sub (keys %$subs){

        print "\nSub: $sub\n";

        for my $line (@{ $subs->{$sub} }){
            my ($line_num, $text) = each %$line;
            say "Line num: $line_num";
            say "Code: $text\n";

The structures look a bit differently when 'file' is a directory. You need to add one more layer of extraction.

    my $files = $des->objects;

    for my $file (keys %$files){
        for my $sub (@{$files->{$file}}){

Print all subs within each Perl file under a directory

    my $files = $des->all( file => 'lib/Devel/Examine' );

    for my $file (keys %$files){
        print "$file\n";
        print join('\t', @{$files->{$file}});

Most methods can include or exclude specific subs

    my $has = $des->has( include => ['dump', 'private'] );

    my $missing = $des->missing( exclude => ['this', 'that'] );

    # note that 'exclude' param renders 'include' invalid


See the "PARAMETERS" for the full list of params, and which ones are persistent across runs using the same object.


Mandatory parameters: file => $filename

Instantiates a new object. If $filename is a directory, we'll iterate through it finding all Perl files. If $filename is a module name (eg: Data::Dump), we'll attempt to load the module, extract the file for the module, and load the file. CAUTION: this will be a production %INC file so be careful.

Only specific params are guaranteed to stay persistent throughout a run on the same object, and are best set in new(). These parameters are file, extensions, maxdepth, cache, regex, copy, no_indent, backup and diff.

Note: omit the file parameter if all you'll be using is the module() method.


Mandatory parameters: None

Returns an array reference containing the names of all subroutines found in the file, listed in the order they appear in the file.


Mandatory parameters: search => 'term'

Returns an array reference containing the names of the subs where the subroutine contains the search text.


Mandatory parameters: search => 'term'

The exact opposite of has.


Mandatory parameters: search => 'text'

Gathers together all line text and line number of all subs where the subroutine contains lines matching the search term.

Returns a hash reference with the subroutine name as the key, the value being an array reference which contains a hash reference in the format line_number => line_text.


Mandatory parameters: None

Optional parameters: objects_in_hash => 1

Returns an array reference of subroutine objects. If the optional objects_in_hash is sent in with a true value, the objects will be returned in a hash reference where the key is the sub's name, and the value is the sub object.

See "SYNOPSIS" for the structure of each object.


Mandatory parameters: 'Module::Name'. Note that this is one public method that takes its parameter in string format (as opposed to hash format).

Note that this method pulls the subroutine names from the namespace (which may include includeed subs. If you only want a list of subs within the actual module file, send the module name as the value to the file parameter, and use the common methods (all, has, missing etc) to extract the names.

Returns an array reference containing the names of all subs found in the module's namespace symbol table.


After one of the other user methods are called, call this method to get returned to you an array of the names of subs you collected, in the order that they appear in the file. By default, because we use hashes internally, subs aren't ever in proper order.


Mandatory parameters: exec => $cref

Core optional parameter: copy => 'filename.txt'

Coderef should be created in the form sub { $_[0] =~ s/search/replace/; };. This allows us to avoid string eval, and allows us to use any regex modifiers you choose. The $_[0] element represents each line in the file, as we loop over them.


Parameters: exec => $cref, limit => 1

This is the entire file brother to the sub-only search_replace(). The limit parameter specifies how many successful replacements to do, starting at the top of the file. Set to a negative integer for unlimited (this is the default).

The exec parameter is a code reference, eg: my $cref = sub {$_[0] =~ s/this/that/;}. All standard Perl regular expressions apply, along with their modifiers. The $_[0] element represents each line in the file, as we loop over them.

Returns the number of lines changed in file mode, and an empty hashref in directory mode.


Mandatory parameters: search => 'this', code => \@code

Injects the code in @code into the sub within the file, where the sub contains the search term. The same indentation level of the line that contains the search term is used for any new code injected. Set no_indent parameter to a true value to disable this feature.

By default, an injection only happens after the first time a search term is found. Use the injects parameter (see "PARAMETERS") to change this behaviour. Setting to a positive integer beyond 1 will inject after that many finds. Set to a negative integer will inject after all finds.

The code array should contain one line of code (or blank line) per each element. (See "SYNOPSIS" for an example). The code is not manipulated prior to injection, it is inserted exactly as typed. Best to use a heredoc, __DATA__ section or an external text file for the code.

Optional parameters:


See search_replace() for a description of how this parameter is used.


How many injections do you want to do per sub? See "PARAMETERS" for more details.


Parameters (all are mutually exclusive, use only one):

line_num => 33 with code => \@code or, inject_use => ['use Module::Name', 'use Module2::Name'] or, inject_after_sub_def => ['code line 1;', 'code line 2;']

line_num will inject the block of code in the array reference immediately after the line number specified.

inject_use will inject the statements prior to all existing use statements that already exist in the file(s). If none are found, will inject the statements right after a Package statement if found.

Technically, you don't have to inject a use statement, but I'd advise it.

inject_after_sub_def will inject the lines of code within the array reference value immediately following all sub definitions in a file. Next line indenting is used, and sub definitions with their opening brace on a separate line than the definition itself is caught.


Parameters: delete => ['string1', 'string2']

Deletes from the file(s) the entire lines that contain the search terms.

This method is file based... the work happens prior to digging up subs, hence exclude, include and other sub-based parameters have no effect.


Configure whether to make a filename.bak copy of all files read by DES. A true value sent in will enable this feature, a false value will disable it. Returns 1 (true) if this feature is enabled, and 0 (false) if not.

Disabled by default.



Returns a hash where the keys are valid parameter names, and the value is a bool where if true, the parameter is persistent (remains between calls on the same object) and if false, the param is transient, and will be made undef after each method call finishes.


Parameter format: Hash reference

All public methods call this method internally. This is the only public method that takes its parameters as a single hash reference. The public methods set certain variables (filters, engines etc). You can get the same effect programatically by using run(). Here's an example that performs the same operation as the has() public method:

    my $params = {
            search => 'text',
            post_proc => 'file_lines_contain',
            engine => 'has',

    my $return = $des->run($params);

This allows for very fine-grained interaction with the application, and makes it easy to write new engines and for testing.




Optional, File::Edit::Portable object.

On first call, a File::Edit::Portable object must be sent in. On subsequent calls, we'll return this object.

Returns: File::Edit::Portable object if previously sent in, else returns undef.




Optional, File::Temp object, typically generated through a call to File::Edit::Portable's tempfile().

On first call, a Temp::File object must be sent in. On subsequent calls, we'll return that object.

Returns: Temp::File object if previously sent in, else returns undef.


WARNING!: This method is for development of this distribution only!

While writing new processors, set the processor type to a callback within the local working file. When the code performs the actions you want it to, put a comment line before the code with #<des> and a line following the code with #</des>. DES will slurp in all of that code live-time, inject it into the specified processor, and configure it for use. See examples/ for an example of creating a new 'engine' processor.

Returns 1 on success.



Informs the system which type of processor to inject and configure. Permitted values are 'pre_proc', 'post_proc' and 'engine'.


Set to a true value, will update the code in the actual installed Perl module file, instead of a local copy.

Optional parameters:


Set it to a new file name which will be a copy of the specified file, and only change the copy. Useful for verifying the changes took properly.

pre_procs, post_procs, engines

For development. Returns the list of the respective built-in callbacks.


There are various parameters that can be used to change the behaviour of the application. Some are persistent across calls, and others aren't. You can change or null any/all parameters in any call, but some should be set in the new() method (set it and forget it).

The following list are persistent parameters, which need to be manually changed or nulled. Consider setting these in new().


State: Persistent

Default: None

The name of a file, directory or module name. Will convert module name to a file name if the module is installed on the system. It'll require the module temporarily and then 'un'-require it immediately after use.

If set in new(), you can omit it from all subsequent method calls until you want it changed. Once changed in a call, the updated value will remain persistent until changed again.


State: Persistent

Default: Disabled

Set this to a true value to have a .bak file copy created on all file reads. The .bak file will be created in the directory the script is run in.


State: Persistent

Default: ['*.pm', '*.pl')]

By default, we load only *.pm and *.pl files. Use this parameter to load different files. Only useful when a directory is passed in as opposed to a file. This parameter is persistent until manually reset and should be set in new().

Values: Array reference where each element is the names of files to find. Any wildcard or regex that are valid in File::Find::Rule's are valid here. For example, [qw(*.pm *.pl)] is the default.


When running in directory mode, how many levels deep do you want to traverse? Default is unlimited. Set to a positive integer to set.


State: Persistent

Default: Undefined

If multiple calls on the same object are made, caching will save the file/directory/sub information, saving tremendous work for subsequent calls. This is dependant on certain parameters not changing between calls.

Set to a true value (1) to enable. Best to call in the new method.


State: Persistent

Default: None

For methods that write to files, you can optionally work on a copy that you specify in order to review the changes before modifying a production file.

Set this parameter to the name of an output file. The original file will be copied to this name, and we'll work on this copy.


State: Persistent

Default: Enabled

Set to a true value, all values in the 'search' parameter become regexes. For example with regex on, /thi?s/ will match "this", but without regex, it won't. Without 'regex' enabled, all characters that perl treats as special must be escaped. This parameter is persistent; it remains until reset manually.


State: Persistent

Default: Disabled

In the processes that write new code to files, the indentation level of the line the search term was found on is used for inserting the new code by default. Set this parameter to a true value to disable this feature and set the new code at the beginning column of the file.


State: Persistent

Not yet implemented.

Compiles a diff after each edit using the methods that edit files.

The following parameters are not persistent, ie. they get reset before entering the next call on the DES object. They must be passed in to each subsequent call if the effect is still desired.


State: Transient

Default: None

An array reference containing the names of subs to include. This (and exclude) tell the Processor phase to generate only these subs, significantly reducing the work that needs to be done in subsequent method calls.


State: Transient

Default: None

An array reference of the names of subs to exclude. See include for further details.

Note that exclude renders include useless.


State: Transient

Default: 1

Informs inject_after() how many injections to perform. For instance, if a search term is found five times in a sub, how many of those do you want to inject the code after?

Default is 1. Set to a higher value to achieve more injects. Set to a negative integer to inject after all.

pre_proc_dump, post_proc_dump, engine_dump, cache_dump, core_dump

State: Transient

Default: Disabled

Set to 1 to activate, exit()s after completion.

Print to STDOUT using Data::Dumper the structure of the data following the respective phase. The core_dump will print the state of the data, as well as the current state of the entire DES object.

NOTE: The 'post_proc' phase is run in such a way that the filters can be daisy-chained. Due to this reason, the value of post_proc_dump works a little differently. For example:

    post_proc => ['one', 'two'];

...will execute filter 'one' first, then filter 'two' with the data that came out of filter 'one'. Simply set the value to the number that coincides with the location of the filter. For instance, post_proc_dump => 2; will dump the output from the second filter and likewise, 1 will dump after the first.

For cache_dump, if it is set to one, it'll dump cache but the application will continue. Set this parameter to an integer larger than one to have the application exit immediately after dumping the cache to STDOUT.

pre_proc_return, post_proc_return, engine_return

State: Transient

Default: Disabled

Returns the structure of data immediately after being processed by the respective phase. Useful for writing new 'phases'. (See "SEE ALSO" for details).

NOTE: post_proc_return does not behave like post_proc_dump. It will only return after all post_procs have executed.


State: Transient

Default: Disabled

Prints to STDOUT with Data::Dumper the current state of all loaded configuration parameters.

pre_proc, post_proc, engine

State: Transient

Default: undef

These are mainly used to set up the public methods with the proper callbacks used by the run() command.

engine and pre_proc take either a single string that contains a valid built-in callback, or a single code reference of a custom callback.

post_proc works a lot differently. These modules can be daisy-chained. Like engine and pre_proc, you can send in a string or cref, or to chain, send in an aref where each element is either a string or cref. The filters will be executed based on their order in the array reference.



CPAN Testers:


If Devel::Trace::Subs is installed, you can configure stack tracing.

In your calling script, set $ENV{DES_TRACE} = 1.

See perldoc Devel::Trace::Subs for information on how to access the traces.


perldoc Devel::Examine::Subs::Preprocessor

Information related to the 'pre_proc' phase core modules.

perldoc Devel::Examine::Subs::Postprocessor

Information related to the 'post_proc' phase core modules.

perldoc Devel::Examine::Subs::Engine

Information related to the 'engine' phase core modules.


Steve Bertrand, <steveb at>


You can find documentation for this module with the perldoc command.

    perldoc Devel::Examine::Subs


Copyright 2016-2020 Steve Bertrand.

This program is free software; you can redistribute it and/or modify it under the terms of either: the GNU General Public License as published by the Free Software Foundation; or the Artistic License.

See for more information.