# e.g @lines1 contains CACTATGAGTGATCGC and @lines2 contains
# ACTGACTAATGCGTTG.

foreach $base (@lines1, @lines2)  {

 shift @lines1;
 shift @lines2;

  if (@lines1[0] eq @lines2[0])  {
  
      last;
  }

  else {

 print "*\n";

 }
}