short answer -- look at use Data::Dumper; print Dumper \%INC; or Module::Depends or Module::ScanDeps (which is what PAR uses--can always just use pp and see what it bundles up).
long answer -- browse these nodes:
And on a related topic:

In reply to Re: What modules does my code require? by davidrw
in thread What modules does my code require? by beth

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