It appears in your code that you set $bool to undef if the regex does match. Do the elements in @_ describe input that you want to keep, or that you want to reject?

In any case, your code will accept or reject based only on the last element of @_. If the regex matches, $bool will be undef, and if the regex doesn't match, $bool will be true, regardless of how all the previous regexes turned out.

As soon as you know you want to accept/reject input, you should last out of the loop. For example:

sub getline {
  my $line = <>;
  chomp $line;

  if (@_) {
    my $reject;

    for (@_) {
      if ($line =~ /$_/) {
        $reject = 1;
        last;
      }
    }
    $line = undef if $reject;
  }
  return $line;
}
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