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Postings from January 2021
On Tue, Jan 12, 2021, at 3:40 PM, Corwin Brust wrote:
> I wonder if you could be running into an entry in %ENV with a undef
> value? In that case we could end up with an odd number of
> hash-elements and worse. Perl will ignore the undef values from
> hashes "exploded" within parens, e.g. within the ... part of @x = (
> ... ). When we come to assign the resulting list back into a new hash
> we then get "misalignments".
That is incorrect.
use v5.30.0;
my %hash = (a => undef, b => 1);
my @array = %hash;
my %other = @array;
use Data::Dumper;
print Dumper(\%other);
Output:
$VAR1 = {
'a' => undef,
'b' => 1
};
You may be thinking of the common mistake where someone puts a subroutine call into a hash assignment:
%hash = (
a => subroutine(),
b => 1,
);
In that case, subroutine() may return something other than a single element, which could be surprising. If it returns an even number of elements, it also throws b from the key position to the value position. In that case, you generally want to put "scalar" before subroutine.
undef is already a scalar value. It does not cause this problem.
--
rjbs
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