AFAIK, Perl uses the standard PATH environment variable, which may not be what you expect it to be if you're running the webserver under its own user account.
As far as finding the file, your package manager may list it (if you installed it through there, rather than CPAN), or you can use find. I don't generally use find (I'm lazy and use locate, which isn't available on Solaris iirc), but this should work:
find / -name any-perl.pm
Installation
Solaris installation
This forum has a limit to the number of forum postings you can make in a given time period - this is currently set at 5 posting(s) in 1 day