Re^4: Syntax question about closures and Perl 'sort'

Actually that is not quite right. If a variable is not visibly used in a returned subroutine, Perl cleans it up. You can verify that with this example:

sub create_closure {
  my $x = "x";
  my $y = "y";
  return sub {
    $y .= "y";
    eval q{print "x: $x\ny: $y\n"};
  };
}

create_closure()->();
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And you will find that $x is not properly remembered, but $y is.

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Re^5: Syntax question about closures and Perl 'sort' by jethro (Monsignor) on Apr 05, 2009 at 18:43 UTC
Interesting fact of the disturbing kind ;-) The language designer or a programmer in that language would still call it a closure. That the implementation optimized it away would (normally) only interest the implementor of the language. That it can be revealed through an eval I would call an implementation bug. Ideally any optimization must not change the result of a programm execution.	[reply]