#!/usr/bin/perl -l

use strict;
use warnings;

while(<DATA>){
  chomp;
  print;
  print /\b\@testing\b/ ? "Matched \\b" : "Did not match \\b";
  print /\B\@testing\b/ ? "Matched \\B" : "Did not match \\B";
  print "";
}

__DATA__
@testing
foo@testing
foo @testing