while(my $line51 = <$ifh51>) {
   # my $line51 = $_ if /\bbist_mode\b/;
  @result = grep (/bist_mode/, $line51);
  @result1 =  grep (/mode_sel/, $line51);
  @result2 = grep (/mem_type_sel/, $line51);

    $b = join("_",@result);
    $b =~ s/,([^,]*$)/$1/;
    $c = join("_",@result1);
    $c =~ s/,([^,]*$)/$1/;
    $d = join("_",@result2);
    $d =~ s/,([^,]*$)/$1/;
    print $b;
    print $c;
    print $d;
  }