Just a few remarks (though i've got a sneaking suspicion i'm correcting typos here):

> my $i ||=0 ;
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here $i will always turn out to be 0 (because of the my operator), so my $i=0; is more efficient.

> $i?$i=1:$i=0;
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How about $i=$i?1:0; - that's also a bit more readable. (at least to my eyes).

Joost.