for( my $r=0;$r<@rres;$r+=5 ) { for( my $l=0;$l<@lres;$l+=5) { my $fam_listen = $lres[$l]; next if $rres[$r] != $fam_listen; # must be same family push @flr,[ $fam_listen,$lres[$l+3],$rres[$r+3] ]; } }