I've found the shell script by
jhourcle at
Re: Which module did I load? very helpful. It not only tells you which of multiple copies in your @INC path is the module perl is using, it gives you the version number and the other modules that will be loaded with it. Here's his sample invocation and partial output, copied from the node in the link.
$ whichpm CGI
CGI.pm : /System/Library/Perl/5.8.6/CGI.pm
CGI/Util.pm : /System/Library/Perl/5.8.6/CGI/Util.pm
Carp.pm : /System/Library/Perl/5.8.6/Carp.pm
...