#!/usr/bin/perl
use strict;
use warnings;

my $outs = <<'EOS';
A B C
A B D
A D E
EOS


if ( (()=$outs =~ m|D|g)==2) { print "exactly 2 matches for D\n" }

# I think better written as:

my @matches = $outs =~ m|D|g;
print "exactly 2 matches for D\n" if @matches ==2;