http://www.perlmonks.org?node_id=1222946


in reply to goto HACK

use strict;
use warnings;
use Data::Dumper;

my @times = qw(1000 1000 1000 1010 1010 1010);
my $hash = {};

for my $time (@times) {
    $time++ while exists $hash->{$time};
    $hash->{$time}->{one} = 1;
    $hash->{$time}->{two} = 2;
}
print Dumper $hash;

[download]
Note that $time++ modifies the element of @times, since 'for' makes $time an alias of each element. If that's undesirable, copy $time to another var at the top of the loop, and use that instead.

Dave.

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Re^2: goto HACK
by Anonymous Monk on Sep 25, 2018 at 09:24 UTC
    Note that $time++ modifies the element of @times, since 'for' makes $time an alias of each element.

    That's kinda creepy! I assumed declaring the var was making a copy of the element that wouldn't change the array. I can't believe I never noticed that... and the same with hash values, but not keys?

[reply]
      Yes, the keys function returns temporary copies of the keys while values returns the actual values. So 
      $_++ for @a;           # modifies each element of @a
$_++ for values %hash; # modifies every value of %hash
$_++ for keys %hash;   # doesn't do anything useful

      [download]

      Dave.

[reply]
[d/l]

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