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Re: What I Most Recently Learned in Perl, But Should Have Already Known

by wfsp (Abbot)
on Aug 17, 2006 at 11:03 UTC ( #567884=note: print w/ replies, xml ) Need Help??


in reply to What I Most Recently Learned in Perl, But Should Have Already Known

Using a foreach loop on an AoH creates an alias of the hash which goes out of scope after the loop.

#!/usr/bin/perl use strict; use warnings; my $recs = [ # short records for brevity {id => 1}, {id => 2}, {id => 3}, ]; my $rec; for $rec (@{$recs}){ # $rec is an alias... if ($rec->{id} == 1){ last; } } # ... which is now out of scope :-( print "$rec->{id}\n"; # Use of uninitialized value... # what I should have done ($rec) = grep {$_->{id} == 1} @{$recs}; print "$rec->{id}\n"; # 1


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Re^2: What I Most Recently Learned in Perl, But Should Have Already Known
by pKai (Priest) on Aug 17, 2006 at 22:55 UTC
    # $rec is an alias...

    It's the previously declared lexical, implicitly localized. See perldoc perlsyn...

    Shorter example, without the need to blame AoH for the problem:

    my $var = 4; for $var (1 .. 9) { last if $var == 7; } print $var; # prints: 4

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