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Re: global variable initialization inside try{}

by ikegami (Pope)
on Apr 09, 2009 at 15:39 UTC ( #756640=note: print w/ replies, xml ) Need Help??


in reply to global variable initialization inside try{}

First, keep in mind that
try { ... } ...
is the same thing as
try sub { ... }, ...
and that's the source of many problems.

$GLOBAL_VARIABLE falls out of scope at the end of the (.pm) file, and before 5.10.0, a reference by an anon sub isn't enough to to keep it alive.

Simplified test case:

use strict; use warnings; { my $f = 'test'; my $g = 'test'; sub f { sub { print "f: $f\n" }->(); } sub g { $g if 0; sub { print "g: $g\n" }->(); } } f(); g();
>perl589\bin\perl test.pl Use of uninitialized value in concatenation (.) or string at test.pl l +ine 9. f: g: test >perl5100\bin\perl test.pl f: test g: test

Note that adding a reference to the captured variable in the named sub — even one that's optimized away — makes it available to the anonymous sub.

A similar problem exists with eval '$s'. While not fixed, a warning was added in 5.10.0.

>perl589\bin\perl -wle"{ my $s='test'; sub f { print 's: ', eval '$s' +} } f()" Use of uninitialized value in print at -e line 1. s: >perl5100\bin\perl -wle"{ my $s='test'; sub f { print 's: ', eval '$s' + } } f()" Variable "$s" is not available at (eval 1) line 2. Use of uninitialized value in print at -e line 1. s:


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