Hash Keys and Values
Learn how to check for the existence of hash keys and how to access them.
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Checking hash key existence
The exists operator returns a boolean value to indicate whether a hash contains
the given key:
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my %addresses = (Leonardo => '1123 Fib Place',Utako => 'Cantor Hotel, Room 1');say "Have Leonardo's address" if exists $addresses{Leonardo};say "Have Warnie's address" if exists $addresses{Warnie};
Using exists instead of accessing the hash directly avoids two problems. First,
it doesn’t check the boolean nature of the hash value; a hash key may exist
with a value even if that value evaluates to a boolean false (including undef):
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use Test::More;my %false_key_value = ( 0 => '' );ok %false_key_value,'hash containing false key & value should evaluate to a true value';done_testing();
Second, exists avoids