Depending on how you want to use the information this may help:
use Benchmark qw( cmpthese );
$s = join'', map{ chr( 65+rand(26) ) x rand( 100 ) } 1 .. 1000;;
push @first, $1 while $s =~ /((.)\2*)/gs;
$s2 = " $s" ^ $s; # XORing the string with a shifted copy of itself, s
+o that you have a series of 0s for identical characters
push @second, $1 while $s2 =~ /(.\o{0}*)/gs;
$\ = $/ x 2;
print pack "(A4)*", map length, @first;
print pack "(A4)*", map length, @second;
cmpthese -1,{
a=>q[
1 while $s =~ m[((?=(.))\2+)]g;
],
b=>q[
1 while $s =~ m[((.)\2*)]sg;
] ,
c=>q[$s3 = " $s" ^ $s;; 1 while $s3 =~ /(.\o{0}*)/gs],
};;
This first prints the length of the strings found by the two methods (I have removed most of the lines, which don't add any more information):
55 97 65 7 87 60 53 98 2 71 35 68 67 58 12 19 17 22
+ 5 28 63 96 30 18 32 6 37 27 47 68 79 97 2 9 60
+ 75 87 31 15 82 62 78 33 69 10 35 4 82 61 33 63 82
+96 68 140
88 59 67 87 78 98 14 3 6 52 59 74 86 79 49 44 28 76
+ 25 83 99 66 42 67 73 3 46
55 97 65 7 87 60 53 98 2 71 35 68 67 58 12 19 17 22
+ 5 28 63 96 30 18 32 6 37 27 47 68 79 97 2 9 60
+ 75 87 31 15 82 62 78 33 69 10 35 4 82 61 33 63 82
+96 68 140
88 59 67 87 78 98 14 3 6 52 59 74 86 79 49 44 28 76
+ 25 83 99 66 42 67 73 3 46 1
So the second method does give the correct length (plus an extra character because of the shift).
And the benchmark is much faster:
Rate a b c
a 445/s -- -4% -80%
b 465/s 5% -- -79%
c 2228/s 401% 379% --
It does not provide all the information of other methods directly (you still have to get a character in the original string to know what a substring exactly is), but might be useful depending on what you actually need.
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