I see that your question has been answered. I just want to point out that the %$a = { %$a,  %$b }; part makes a copy of %$a and %$b before the assignment, which could be less efficient when the hash sizes are big. The following code works off the reference to %hash directly without making an additional copy of itself.
use strict;
use Data::Dumper;

my %hash1 = qw/ A 1 B 2 /;
my %hash2 = qw/ C 3 D 4 /;

mergetwohashes(\%hash1, \%hash2);
print Dumper(\%hash1);

sub mergetwohashes {
    my ($a, $b) = @_;
    $a->{$_} = $b->{$_} foreach keys %$b;
}

[download]
And the output is as expected -
$VAR1 = {
          'A' => '1',
          'B' => '2',
          'C' => '3',
          'D' => '4'
        };

[download]

In reply to Re: Modify hash reference itself by Roger
in thread Modify hash reference itself by Anonymous Monk

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