That's only if perldoc -l File::Find doesn't work, right? :)

$ 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
             ...
[download]

You may try which_pm as well. It comes with Module-Which distribution and also shows the module version number.

$ which_pm CGI
CGI                  3.15       /usr/local/lib/perl5/5.8.8/CGI.pm

$ which_pm CGI:: --p5p
CGI::Cookie                         1.26       at ${installprivlib}/
CGI::Util                           1.5        at ${installprivlib}/
CGI::Pretty                         1.08       at ${installprivlib}/
CGI::Carp                           1.29       at ${installprivlib}/
CGI::Push                           1.04       at ${installprivlib}/
CGI::Switch                         1.00       at ${installprivlib}/
CGI::Apache                         1.00       at ${installprivlib}/
CGI::Fast                           1.05       at ${installprivlib}/
CGI::Session                        4.20_1     at ${installsitelib}/
CGI::Session::Driver                4.20       at ${installsitelib}/
[SNIP]

from Config:
        installprivlib: /usr/local/lib/perl5/5.8.8
        installsitelib: /usr/local/lib/perl5/site_perl/5.8.8
[download]

I don't know if there's an official way, but here's what I could whip together:

sub find_installed_path {
    my $module_name = shift;
    # For Unix systems:
    $module_name =~ s!::!/!g;
    # For Windows:
    #$module_name =~ s!::!\\!g;
    $module_name .= '.pm';
    foreach my $path (@INC) {
        next if (ref $path);
        return "$path/$module_name" if (-f "$path/$module_name");
    }

    return '';
}

print find_installed_path('File::Find');
[download]

YMMV, but works with Linux and Perl 5.8.8.

UPDATE: @INC may contain references (to subroutines, blessed objects, etc.), so added a check right at the beginning of the foreach loop.

use strict;
use Pod::Simple::Search;
use constant DEBUG => 0;

for (qw(CGI.pm File::PathInfo HTML/Template.pm Smart::Comments)){
    my $name = $_;
    my $returned = lookup_as_perl($name);
    print " ARG: $name = $returned\n";
}


sub lookup_as_perl {
    my $arg_name = shift;
    print STDERR "lookup_as_perl() $arg_name, " if DEBUG; 
    $arg_name=~s/^\/+//; # take out leading slashes
    $arg_name=~s/\/+/\:\:/g;
    $arg_name=~s/\.html$|\.pod$|\.pm$//;
    $arg_name=~s/\/+/\:\:/g;    
    print STDERR "cleaned to $arg_name, " if DEBUG;     
    
    #can we find this?
    my $search = Pod::Simple::Search->new;
    my $result = $search->find($arg_name);

    $result ||= 0;
    
    print STDERR  "result = $result\n" if DEBUG;
    
    return $result;    
}
# returns ...
#[betti@mescaline cgihelp]# perl test.pl
# ARG: CGI.pm = /usr/lib/perl5/5.8.8/CGI.pm
# ARG: File::PathInfo = /usr/lib/perl5/site_perl/5.8.8/File/PathInfo.p
+m
# ARG: CGI::Carp = /usr/lib/perl5/5.8.8/CGI/Carp.pm
# ARG: Smart::Comments = /usr/lib/perl5/site_perl/5.8.8/Smart/Comments
+.pm
# ARG: HTML/Template.pm = /usr/lib/perl5/site_perl/5.8.8/HTML/Template
+.pm
[download]