There is no difference between a "hash reference" and a "hash" in terms of performance. In simple terms, internally a "hash" is just a "name" (global or lexical) with a "hash reference" attached to it internally.

And you don't need a hash reference to pass hashes quickly to subroutines: you can generate references to hashes "on the fly":

foo( \%hash );   # hashref created "on the fly" by taking ref of hash
foo( $hashref );  # use hash reference stored in a scalar
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Both become the same type of hash reference inside  sub foo.

Hope this helps.

Liz