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Thanks for the report.
This is expected behaviour. It isn't actually anything to do with multiprocessing; it's to do with invoking exec from within a function scope. You can see the same effect with code like this:
code = """\
def show_name():
 print my_name
show_name()
"""
def run():
 my_name = "me"
 exec code
run()
See
http://docs.python.org/reference/executionmodel.html#interaction-with-dynamic-features
for more explanation.