my $str = "";
open (FD, "<", "CSD.txt");
my @lines = <FD>;
close FD;

foreach (@lines) {
 if(/GROUP NAME: X[A-Z]../) {
print STDOUT $_;
 $str= $str.$_;
 open (NW, ">", "RES.txt");
print NW $str;
close NW;
}
}