The optree is Perl's internal representation of your code -- bytecode, in Parrot terms. Closures are nice because they all share the same opcodes. (To simplify things perhaps past the point of correctness :), a cv, or code value, is a struct with a pointer to the optree for the function. There's also a pointer to the lexical scratchpad that holds enclosed variables.) The only difference is the lexical pad to which the closure is attached.

If you had a dozen accessors, you could write a dozen subroutines with individual optrees, or you could autogenerate them and use 1/12th the memory with one shared optree and closures.

If you want to modify the optree, you'll have to use the B:: modules and learn a lot more than I know at the moment, or have a lot of luck. :)