This is very simple, but it happens often and I have to write extra code to handle it : 

use Data::Dumper;
my $hashref;
print Dumper $hashref;
if(exists $hashref->{a}->{b}) 
{
# Do something
}
print Dumper($hashref);

[download]

Of course, at the first print $hashref is undef, but after the exists statement $hashref is now: { 'a' => {} } Why ?

In reply to Why does testing for the existence of hash keys create the keys ? by fshrewsb

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