for ($i=1; $i<=3; $i++) {
  open $input1, '<', "$path\/File-$molec1-cluster$i.out" or die $!;
  push @ARGV, "$path\/File-$molec1-cluster$i.out";

  for ($j=2; $j<=3; $j++) {
  open $input2, '<', "$path\/File-$molec2-cluster$j.out" or die $!;

  push @ARGV, "$path\/File-$molec2-cluster$j.out";