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Re^2: why need my in a foreach loop?

by 7stud (Deacon)
on Nov 28, 2010 at 19:59 UTC ( #874133=note: print w/ replies, xml ) Need Help??


in reply to Re: why need my in a foreach loop?
in thread why need my in a foreach loop?

Here's the difference:

use strict; use warnings; use 5.010; our $foo = 'hello'; sub f { print("$foo\n"); } for my $foo (qw( a b c )) { f(); } --output:-- hello hello hello

In ikegami's example, the my is omitted in the for loop, which causes the for loop to change the global variable $foo--and the subroutine prints the global $foo (i.e. the subroutine is a closure).


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Re^3: why need my in a foreach loop?
by ikegami (Pope) on Nov 28, 2010 at 23:23 UTC

    the subroutine is a closure

    Backwards. It works because the subroutine doesn't capture package variables. If you switched our for my in my snippet, you'd have a closure, and you'd get a different result.

      Nice catch.

      If you switched our for my in my snippet, you'd have a closure, and you'd get a different result.

      Is that correct? Because the my variable would still be in scope, would the subroutine qualify as a closure? It's my understanding that a subroutine is a closure when it preserves a variable that has gone out of scope.

        I don't know the precise definition if there is one. For practical purposes, I find it doesn't matter.

        Correction: In this case, the sub truly acts as a closure. If it didn't, it wouldn't matter if you used our or my.

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