I'll probably get shouted at for this because it's so obvious. I have some code which is essentially doing this : 

my %hash = (a => 1, b => 2);
mysub(\%hash);
print Dumper(\%hash)

sub mysub{
my $h = shift;
delete $h->{'b'};
}

[download]

Output :

$VAR1 = {
          'a' => 1
        };

[download]

As mysub() is passed a reference to %hash, why is the global %hash modified ? The only way I can think of to have %hash intact after calling mysub() is to create a copy of %hash using Storable::dclone and pass it to mysub(), but there has to be a simpler way.

In reply to Global variable unexpectedly modified when passed by reference by fshrewsb

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