I believe there's another, more standard, way to do it, but this should do what you want:

use File::Find;
$|++;
find sub { print "$File::Find::name\n" if $_ =~ /\.pm$/ }, @INC;
[download]

Of course, if you don't have File::Find, try:

$|++;
while (@INC) {
    my $dir = shift @INC;
    opendir(MODDIR, $dir) or die "opendir $dir: $!";
    @allfiles = readdir MODDIR;
    foreach (@allfiles) {
        $file = "$dir/$_";
        next if $_ eq '.' or $_ eq '..';
        unshift @INC, $file if -d $file;
        print "$file\n" if $_ =~ m/\.pm$/;
    }
    closedir MODDIR;
}
[download]

-- Frag.