use strict;
use warnings;

open(my $fh_in, '<:raw:encoding(utf16le)', 'src.txt')
   or die("Unable to open src.txt: $!\n");

open(my $fh_out, '>:raw:encoding(utf16le)', 'dst.txt')
   or die("Unable to create file.txt: $!\n");

while (<$fh_in>) {
   if (/[\x{706B}\x{6C34}]/) {
      print("Found one at line $.!\n");
   }

   print $fh_out $_;
}