Your last four lines have several problems

The showstoper? "=" is an assignment. You're looking for "=~"

And once you get your regex right, you can combine the ideas behind your while and print lines, like this:

if ( $line =~ /(regex)/ ) {
      print "$line\n";
} else {
      print "whoops. no match!\n";
[download]

And this may be my bad (for eyes being shot?) but what the heck is your

if $line =~ /_NN/;

supposed to be doing for you? I don't see that string anywhere in your data.

Update: Fixed markup & typos -- thanks to GrandFather for his attention and advice.