See:

FIND_MATCH:
{
  foreach my $a (@array)
  {
    if( $hash{$a} eq 'correct_value' )
    {
      print 'Success';
      last FIND_MATCH;
    }
  }
  warn "Didn't find a suitable match!";
}
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By targeting the last at the outer block, if you find a match, you completely exit that block. Otherwise, if you make it all the way through the foreach loop without a match, you will hit the warning message right before exiting the block.