Perlsecret - Perl secret operators and constants

Perlsecret - Perl secret operators and constants(search.cpan.org)

59 points by yurifury 13 years ago | 18 comments

pyre 13 years ago |

This fails to mention the most useful part of the "baby cart":

  "Greetings @{[ get_planet() ]}lings, we come in peace!"

Evaluating functions directly inside of a string. It's sort of alluded to with "@{[ keys %hash ]}", but in doesn't come right out and say it.

btilly 13 years ago | |

You get the wrong context when you do that. Try it with, say, localtime and see what happens. String interpolation is more obvious, and only one character more in normal formatting, one character less in golf:

    "Greetings " . get_planet() . "lings, we come in peace!"

As it says, the whole point of the baby cart is to force list interpolation. If you don't specifically want that, don't do it.

mst 13 years ago | | |

    "Greetings ${\ get_planet() }lings, we come in peace!"

will give you scalar context as well. My http://shadow.cat/blog/matt-s-trout/madness-with-methods write-up covers some other uses of ${\}

pyre 13 years ago | | |

Depends on what you're doing. In a small string, there isn't much difference. It's more useful when doing other things:

  my $message = <<"HEREDOC";
  Greetings @{[ get_planet() ]}lings,

  We come in peace.
  
  Sincerely,
  Your New @{[ get_invaders() ]} Overlords
  HEREDOC

Sure you can jam them into variables first, or use sprintf, but it's a matter of preference so long as you know what you're doing.

JadeNB 13 years ago |

Peteris Krumins wrote about some of these operators some years ago: http://www.catonmat.net/blog/secret-perl-operators.

nemo1618 13 years ago |

As someone who loves obfuscated Perl...thanks! These are some great tricks.

hippich 13 years ago | |

From someone who loves Perl, please do not use it in production :)

Although, it is really interesting find!

prakashk 13 years ago | | |

While I generally agree that the discretion must be observed when working on production code, I don't think the author is advocating these to be of wide use.

These are very useful when you play Perl Golf, and can be pretty powerful in the hands of an expert player (sadly, my dreams of becoming one has remained just that.)

The author of this document was a regular in Perl Golf tournaments and also in the Fun With Perl mailing list, which was a precursor and launchpad for several of these tournaments.

For those interested, here is a series of articles about "The Lighter Side of Perl Culture": http://www.perlmonks.org/?node_id=410774

See also, "Perlgolf History" at http://terje2.frox25.no-ip.org/perlgolf_history_070109.pdf (not sure if this link is still alive.)

irahul 13 years ago | | |

> From someone who loves Perl, please do not use it in production :)

From another someone who has written fair amount of perl, some of them are simple idioms suitable for production use; rest are just an exercise in curiosity.

The venus operator "0+ $input"(or `0 + $input` as I will write it) is an acceptable and recommended way to convert input to number(i.e if you know your your input is a valid number in string form). !! isn't unique to perl - I have used it in JS, C etc to convert a value to boolean. @{[ ]} is useful for logging, thought it does look difficult to grok in first look. Goatse is basically list assignment and then using it in scalar context; I won't do that but assigning to list is frequently done `my ($a, $b) = $input =~ /regex/`. =<>~ is just badly formatted `my ($a, $b) = <> =~ /regex/` will read fine to a perl programmer.

hahainternet 13 years ago | | |

Very few of these are really unsuitable for production. High preference and conditional operation operators are probably the ones I would be most shocked to see.

The rest (especially goatse, venus and things like X-Wing) should be fairly intuitive from operator precedence.

snorkel 13 years ago |

Part of the reason I've stopped writing Perl apps, the operator noise is getting out of hand.

hahainternet 13 years ago | |

Could you give examples? All of the recent Perl improvements have introduced operators that seem extremely useful to me and reduce noise.

kamaal 13 years ago | |

Proof please.

Don't get me wrong, but comment that start out like this generally turn out to be trolls.

duskwuff 13 years ago | |

None of these are new operators. They're just creative ways of abusing existing operators, most of which aren't even unique to Perl.