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Re: anonymous vs named subroutines as closures

by ikegami (Pope)
on Jun 04, 2013 at 04:16 UTC ( #1036884=note: print w/ replies, xml ) Need Help??

in reply to anonymous vs named subroutines as closures

Demonstration of "will not stay shared":

sub outer { my ($x) = @_; sub inner { say $x; } inner(); } # Warns Variable "$x" will not stay shared outer(4); # Prints 4 outer(6); # Prints 4!!!

Here's what's going on.

sub named { ... }

is more or less the same as

BEGIN { *named = sub { ... }; }

As such, it only captures once, when the sub is compiled.

In the above code, when outer goes out of scope, $x would normally be cleared. But since the closure still references it, a new $x is a created instead. From this point on, the $x in inner is different from the $x is outer; it "didn't stay shared".

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