but it only works for hashes.

As of Perl 5.6.0, the exists function can be used on arrays to test the existence of an element within an array. For example:

my %hash = ( 'key' => 'value' );

print "exists \$hash{'key'}\n" if exists $hash{'key'};

my @array = ( 'value' );

print "exists \$array[\$index]\n" if exists $array[0];
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Under Perl 5.005.03 this code results in an error:

exists operator argument is not a HASH element at test-5.00503.perl li
+ne 7.
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Whereas, under Perl 5.6.0 or later, the code executes without error:

exists $hash{'key'}
exists $array[$index]
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Cool huh? Much nicer than using a construct like ($index <= $#array) to test the existence of an array element - Especially if someone is performing magic with $[ !

perl -e 'print+unpack("N",pack("B32","00000000000000000000000111010111")),"\n"'

Does anyone know how the exists function is implemented for arrays? Is it the equivalent of a linear search through the array, or is it more interesting? Essentially, does it have a worst case time complexity better than N? Oops. Didn't read that very carefully. Thought you could do an exists on a value, not an index.