Devel::Modlist - Perl extension to collect module use information


    perl -d:Modlist


The Devel::Modlist utility is provided as a means by which to get a quick run-down on which libraries and modules are being utilized by a given script.

Just as compiler systems like gcc provide dependancy information via switches such as -M, Devel::Modlist is intended to assist script authors in preparing dependancy information for potential users of their scripts.


Usage of Devel::Modlist is simple. The primary method of invocation is to use the -d option of Perl:

    perl -d:Modlist

Alternately, one could use the -M option:

    perl -MDevel::Modlist

In the case of this module, the two are identical save for the amount of typing (and option passing, see below). It is not recommended that this module be loaded directly by a script via the use keyword, as that would cause the dependancy reporting after every invocation until it was removed from the code.


The following options may be specified to the package. These are specified either by:

    perl -MDevel::Modlist=option1[,option2,...]


    perl -d:Modlist=option1[,option2,...]

Options may also be given in an environment variable, which gets read at any invocation in which there are no options explicitly provided. If any options are given in the invocation, then the environment variable is ignored. Two different names are recognized:


The latter is to accomodate shells that do not like the presence of :: in an environment variable name.

The options:

Reduce the resulting list of modules by using the data maintained in the local CPAN configuration area. The CPAN module (see CPAN) maintains a very thorough representation of the contents of the archive, on a per-module basis. Using this option means that if there are two or more modules that are parts of the same distribution, only one will be reported (the one with the shortest name). This is useful for generating a minimalist dependancy set that can in turn be fed to the CPAN install command to ensure that all needed modules are in fact present.

This is identical to the option above, with the exception that it causes the reported output to be the CPAN filename rather than the module name in the standard Perl syntax. This can also be fed to the CPAN shell, but it can also be used by other front-ends as a path component in fetching the requisite file from an archive site. Since the name contains the version number, this behaves as though noversion (see below) was also set. If both cpan and cpandist are set, this option (cpandist) takes precedence. If path is also specified, this option again takes precedence.

Suppress the display of those modules that are a part of the Perl core. This is dependant on the Perl private library area not being an exact substring of the site-dependant library. The build process checks this for you prior to install.

Suppress the inclusion of version information with the module names. If a module has defined its version by means of the accepted standard of declaring a variable $VERSION in the package namespace, Devel::Modlist finds this and includes it in the report by default. Use this option to override that default.

Display the path and filename of each module instead of the module name. Useful for producing lists for later input to tools such as rpm.

Exit before the first actual program line is executed. This provides for fetching the dependancy list without actually running the full program. This has a drawback: if the program uses any of require, eval or other such mechanisms to load libraries after the compilation phase, these will not be reported.


Perl versions up to 5.6.0 cannot accept options to the -d: flag as with the -M flag. Thus, to pass options one must use:

    perl -MDevel::Modlist=option1[,option2,...]

Unfortunately, this inhibits the stop option detailed earlier. To use this option, an invocation of:

    perl -d:Modlist -MDevel::Modlist=option1[,option2,...]

does the trick, as the first invocation puts the interpreter in debugging mode (necessary for stop to work) while the second causes the options to be parsed and recorded by Devel::Modlist.

Versions of Perl from 5.6.1 onwards allow options to be included with the -d:Modlist flag.


Randy J. Ray <>, using idea and prototype code provided by Tim Bunce <>