Quote:Secondly, $key is an alias to each value in the list, which means modifying $key will modify the original value :EndQuote

It will change the value in the list returned by keys and sort, but not in the original hash, e.g.

my %hash = (1 => 'a', 2 => 'b', 3 => 'c');

foreach my $value (sort keys %hash )
{
    $value--;
}

print join( ', ', sort keys %hash ), "\n"; # 1, 2, 3
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-imran