Given a string of bytes, I want to split the string into chunks of the same byte value, as efficiently as possible. Ie. Given 'aaabcccdeeefffggg', get 'aaa','b','ccc','d','eee','fff','ggg'. The string of bytes can contain *any* values 0 .. 255.

I thought this would be easy, but has actually proved to be quite hard. The fastest, and in fact only way I've found is shown below. Test b checks the cost of the /m modifier, but is just a placeholder for something better... 

$s = join'', map{ chr( 65+rand(26) ) x rand( 100 ) } 1 .. 1000;;

cmpthese -1,{
    a=>q[ 
        1 while $s =~ m[((?=(.))\2+)]g;
    ],
    b=>q[
        1 while $s =~ m[((?=(.))\2+)]mg;
    ] 
};;
   Rate   a   b
a 203/s  -- -1%
b 205/s  1%  --

[download]

Anyone see a better, ie. more efficient way?

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In reply to Faster regex to split a string into runs of similar characters? by BrowserUk

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