It works as per the OP's spec. Don't blame me for his spec being awful!

For strings, 

0+$x;   #Upd: Or 1.1 or whatever

[download]

is effectively 

$x = dualvar(0+$x, $x) if looks_like_number($x);

[download]

The OP was clear that dualvar(0, $anything) should be considered zero.

In reply to Re^3: Determining whether a value is zero. by ikegami
in thread Determining whether a value is zero. by JavaFan

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