For Perl up to and including 5.10, calling split in scalar or void context had the side-effect of setting @_. This mis-feature was removed in Perl 5.12. That was great news for most Perl programmers because this side-effect "feature" was unnecessary, an ugly wart. It was sad news for golfers though because side-effects are frequently useful in golf. In fact, I recently experienced a similar split annoyance in Compression in Golf: Part III, as described in the "Fun with split" section in that node.

Simply changing @_ to @z say should fix thospel's original solution at the cost of three strokes:

$_=$`.$_.$'.<>;@z=split//;${/[@z[map{$i-($i="@-")%9+$_,9*$_+$i%9,9*$_%
+26+$i-$i%27+$i%9-$i%3}0..8]]/o||do$0}for/0/||print..9
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