'next', 'last' out of subroutine

I have been operating for a while under the assumption that an eval {}
around a subroutine will always give you a chance to execute code after the
subroutine is done. However, I've just realized this is not the case: you
can 'next' or 'last' out of subroutine to a loop in the caller. e.g. this
program

   sub bar { next; }
   sub foo { print "starting foo\n"; eval { bar() }; print "finished
foo\n" }
   print "starting loop\n";
   for (1) {
       foo();
   }
   print "finished loop\n";

outputs

   starting loop
   starting foo
   finished loop

under perl 5.6.1. I find it odd since the Perl manual for 'next' and 'last'
says

           [`next'|'last'] cannot be used to exit a block which returns a
value such
            as `eval {}', `sub {}' or `do {}', and should not be used to
            exit a grep() or map() operation.

Am I misinterpreting this statement? I do see that some modules actually
depend on this behavior (e.g. Test::More for its skip() subroutine).

Anyway, the way this relates to Mason is that Request::comp has always
relied on regaining control after its eval {} so that it can clean up its
stack. But if you have a loop in one component, and a 'next' or 'last' in
its child component, you can skip Mason's cleanup code entirely and end up
with a corrupted stack.

If this is a Mason "bug", it'll be a real pain to fix - we'll have to
rewrite every bit of code that depends on a reliable exit from eval {}.
Bleah.

Jon



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