in reply to File-scoped lexicals and eval scope?

There is an implicit {} block round any file. When you use TestMeNow, the code in the file is compiled and executed, then at the end of execution, %map and $value go out of scope and are freed. Later you call initialize(), which within the eval, attempts to find the current value of $value and gets undef. In perl 5.10.0-to-be, if you enable warnings you get the following warning when that happens: 
Variable "$value" is not available at (eval 1) line 1, <DATA> line 1.

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Dave.

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Re^2: File-scoped lexicals and eval scope?
by ysth (Canon) on Nov 09, 2007 at 04:51 UTC
    %map and $value go out of scope, but are not freed, since initialize closes over %map which references $value. But since the implicit file scope was exited and initialize does not close over $value, in the call to initialize, $value is no longer bound to initialize's %map's ${$map{value}} and so is "not available". Correct?

    Inserting a $value if 0; into sub initialize to make it close over $value and correcting the 'ex'/'example' inconsistency makes it work (both on 5.8.x and 5.10).

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      Good analysis on what was happening to $value.

      But if the OP wants persistent, file-scope variables, I'd say that package variables are a better choice.

      Changing the 'my' to 'our' would arrange that and be more readable than relying on tricks like 'if 0', imho.

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[d/l]
        That's the conclusion that we came to, finally, which is why the "fix" worked. It just didn't seem to be very intuitive with what we thought we knew about file-scoped lexicals. I never use package variables for this sort of thing, since those can be changed from anywhere, and I really don't like tracking down "action from a distance" issues. In this case, though, it may be the right solution. Thanks for the suggestion! Cambo
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        I guess I don't consider $value if 0; a trick. The idea is that, if sub initialize wants to have its use of $value be bound to the outer lexical even after that lexical's scope is exited, it needs to explicitly mention it. scalar($value); works as well, as does 0 if $value;.  Any of them should be accompanied by a comment. If you want to be pedantic, the latter is best documented as not triggering a 'Useless use' warning.
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