... or you could use my Test::Trap. :)

use Test::More tests => 1;
use Test::Trap;
trap {
  print 'gabba gabba hey';
};
ok($trap->stdout eq 'gabba gabba hey') 
  || diag "didn't print 'gabba gabba hey' to stdout.";
[download]

Edit: On second thought, $trap->stdout_is('gabba gabba hey') may be more than you want. The good news is that ->stdout, as above, gives you all you were asking for.