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

[wfsp]

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

[pKai]

# $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