my @result;
my @result1;
my @result2;
my $b;
my $c;
my $d;

my $ifile51 = '../test.txt';
my $ofile51 = 'seq.txt';

open (my $ifh51, '<', $ifile51) or die $!;
open (my $ofh51, '>', $ofile51) or die $!;
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;
  }
  print $b;
  print $c;
  print $d;