No idea why it worked... my typeglob-fu is somewhat weak. I just happened to notice it while fiddling around with your example. Here are some smallest-case scenerios:

#### in 5.6.1  *F  works, but  \*F  fails
% perl5.6.1 -we'{local *F; $tmp=*F; open F,">out"}  print $tmp $tmp'; 
% cat out
*main::F

% perl5.6.1 -we'{local *F; $tmp=\*F; open F,">out"}  print $tmp $tmp';
print() on unopened filehandle F at -e line 1.
[download]

-Blake