You can't do that. You're best solution is to use a different datastructure.

About your ideas:

• Perl isn't C. Perl doesn't have pointers, so you can't decrement a pointer. And you cannot get to the pointers at the C level, unless you write in XS (or Inline::C). But internally, the hash isn't stored as a single array with alternating keys and values. The structure is far more complex.
• You cannot take the reference of a hash key. Hash keys aren't normal values.

Abigail