while ($a < $b) if not $error
 { $a++; }

[download]
is the same as 
while ($a < $b) if not $error{ $a++; }

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so the parser thinks you are asking for %error with key "$a++;".

Why not: 

(not $error) and $a = $b;

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In reply to Re: backwards if and while looping by johnnywang
in thread backwards if and while looping by jcpunk

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