Re: perl grep

The "fat arrow" => is often also called the "fat comma", because it functions the same as the comma. So the following two pieces of code are the same, functionally:

  grep /regex/ => @_;
  
  # and

  grep /regex/, @_;
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I think that perldoc perlop discusses the peculiarities of the fat arrow, but for many cases, you can simply replace the arrow by a comma.

perl -MHTTP::Daemon -MHTTP::Response -MLWP::Simple -e ' ;    # The  
$d = new HTTP::Daemon and fork and getprint $d->url and exit;#spider
($c = $d->accept())->get_request(); $c->send_response( new   #in the
HTTP::Response(200,$_,$_,qq(Just another Perl hacker\n))); ' #  web
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Comment on Re: perl grep Select or Download Code

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Re: Re: perl grep by RandomWalk (Beadle) on Nov 22, 2003 at 17:15 UTC
Ouch! I knew `=>` was a comma in hash definition from the Llama but I didn't make the connection, sorry. But why would an author be using this form `unless (grep /regexp/ => @_) {...}` [download] ? Is it just easier to read than it would be using a simple comma? Or does the special property of interpreting the word to the left of `=>` as a string have a beneficial effect? Thank you for your kind help.	[reply] [d/l] [select]
Re: Re: Re: perl grep by Corion (Patriarch) on Nov 22, 2003 at 17:27 UTC
I think the fat comma is used here for aestethical reasons, as `/regexp/` is applied to @_. I am also guilty of that sometimes. The notation makes sense sometimes, originally for key-value pairs in hashes : `my %hash = ( foo => bar );` [download] You can also use it for the parameters if you have a subroutine that acts as a pipeline : `sub transform { my ($source, $target) = @_; ... }; transform( 'input/start.file' => 'output/' );` [download] In that case, the "arrow" could be interpreted also in the mapping sense. `perl -MHTTP::Daemon -MHTTP::Response -MLWP::Simple -e ' ; # The $d = new HTTP::Daemon and fork and getprint $d->url and exit;#spider ($c = $d->accept())->get_request(); $c->send_response( new #in the HTTP::Response(200,$_,$_,qq(Just another Perl hacker\n))); ' # web` [download]	[reply] [d/l] [select]