sweepy838 has asked for the wisdom of the Perl Monks concerning the following question:

such a simple thing, from my tutorials there is nothing wrong with this code. 
$input = "-lalala:lalala- hello";

#if "badinput" isnt in the string then print the string.
if (!$input =~ m/badinput/) {
   print "$input!";
}

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ripping my hair out :/

Replies are listed 'Best First'.
Re: totally lost
by JavaFan (Canon) on Apr 29, 2012 at 16:22 UTC
    Precedence. You're matching badinput against the negation of $input. Use: 
    if ($input !~ /badinput/) { ... }

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    instead.

    Or 

    if (!($input =~ /badinput/)) { ... }

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    but that's more typing, and less idiomatic.
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Re: totally lost
by moritz (Cardinal) on Apr 29, 2012 at 16:33 UTC

    Another way to write it: 

    unless ($input =~ /badinput/) {
    print $input;
}

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    Or even 

    print $input unless $input =~ /badinput/;

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    With perl 5.10 or newer you can also write 

    use 5.010;

given ($input) {
    print unless /badinput/;
}

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    Though usually it is a better idea to check for valid input (whitelisting) than checking for bad input (blacklisting).

    Perl 6 - the future is here, just unevenly distributed
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      You do not need given, for/foreach is enough and works even in ancient perls.

      for ($input) {
    print unless /badinput/;
}

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      Jenda
      Enoch was right!
      Enjoy the last years of Rome.

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