Glenn,
Not sure where Will was going with that...

Your examples don't align with what you're saying. The following code:
code:
$X = "first"
? "X=$X, Y=$Y" ?
get $_
$X = "first"
? "X=$X, Y=" + $Y ?
get $_
outputs the following:
quote:
X=first, Y=$Y

X=first, Y=
but you say "I would expect the interpreter to recognize $Y as an uninitialized variable and output Null, but it outputs "$Y" again".
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