You're only doing half the work now :-)

You can make it work like this though: 

++$count{$1},pos($genome)-- while $genome =~ /\G(..)/g

[download]
It's interesting that this is slightly faster than dropping the \G.

This however turns out to be a lot slower (seems to do a complete linear search for the proper string start every time): 

$genome =~ /./g;
$count{$1}++ while $genome =~ /(.\G.)/g

[download]

update This however means that the lookahead version can be speeded up by about 5% too: 

$count{$1}++ while $genome =~ /\G(?=(..))./g

[download]

In reply to Re^3: using s/// as map? by thospel
in thread how can I speed up this perl?? by Anonymous Monk

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