I havent read the rest of the thread, I only comment because of your mistake in the cb ;-), but the test you describe:

if ( defined($foo) and $foo eq '?' ) { 
    print "\$foo OK!\n"; 
}
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Would be better (Lazier) written

print "\$foo OK!\n" 
   if $foo and $foo eq '?';
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in my opinion anyway...

Note that since $foo must be a '?', then it cant be _any_ false value, defined being only one of three. Thus you can dispose of the defined test and replace it with simple true or false.

Yves / DeMerphq
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Software Engineering is Programming when you can't. -- E. W. Dijkstra (RIP)