I don't know if you can use a split here, because your pattern may not consume characters to achieve what you want.

I've tried this one: m/((?<=.))(?!\1)/ which should be "a position before which there is a character, and after that a different character", but it doesn't work.

Can anybody tell me why this doesn't match the string 'aaabbbc'?

Update: Zoffix told me on IRC that the right thing would be m/(?<=(.))(?!\1)/ (because the assertion is zero-width), however that doesn't work in split as well, because it returns the captured character:

$ perl -MData::Dumper -wle '$Data::Dumper::Indent=0; $_="aaabbc"; prin
+t Dumper([split m/(?<=(.))(?!\1)/]);'
$VAR1 = ['aaa','a','bb','b','c','c'];
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This way you had to discard every second item of the returned list - not pretty either ;-)