To start with my $$_ = $_; isn't even valid syntax. You're trying to declare a lexical with a dynamically generated name. Aside from the fact that the lexical would go out of scope when the block was exited (i.e. immediately in this case), it's a syntax error. A more recent perl (5.8.6) would tell you:

Can't use global $_ in "my" at spoo line 11, near "$$_ "
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The real question is what do you think you're trying to accomplish with this. You have $data{blah} already, just use the hash you've got.