It's essentially the same program, with a different comparison:

my $filename = '/Users/Pabli/Desktop/do_human_mapping.gmt';
my $match = 'IL4';

open(my $file, '<', $filename) or die "open: $!";

while (<$file>){
   my ($name,$id,@genes) = split /\t/;
   print $id,$/ if grep/^$match$/, @genes;
}
[download]

Happy to help, but the hope is that you're working towards being able to construct these lil programs for yourself!

Thanks a lot "Loops" you are amazing!!!