Based on your idea, I got it to 38: 
# 34567890123456789012345678901234567890
$_=$_[0]**2;pos=y///c/2;//g;$`+$'==pop

[download]
(Edit: and using thospel's "@_" instead of $_[0] makes it 37. I wonder how I managed to miss that...)

In reply to Re^2: [golf] Kaprekar Numbers by truedfx
in thread [golf] Kaprekar Numbers by jynx

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