#!/usr/bin/perl -w
use strict;

my $String = "Noo S pro NpppT Nop| NPP";
my $LongString = "YYY DDD $String RRR PPP";
my $Pattern1 = qr{N[^P]{2,4}[S|T]};
my $Pattern2 = qr{DDD\s};
for my $m ( $LongString =~ m{($Pattern1|$Pattern2)}g ) {
    print "Yes! $m\n";
}
__END__

Yes! DDD 
Yes! Noo S
Yes! NpppT
Yes! Nop|
[download]

Because it's interesting, and potentially of use, I point you to Why I like functional programming by tilly.

I suggest you give a good gander to all of the links I provided you with (you might not get instant satisfaction, but you'll find 'em all useful, even if it takes a little while)