It shows some odd behaviour if you have duplicate numbers in your input array.

qw( 20 2 3 4 5 6 7 23 19 5 17 25 30 11 4 12 22 5 21 68 103829 24 18 )

results in

103829->0
2->2
4->1
11->1
5->2
68->0
30->0
17->8
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It seems duplicate numbers start new sequences but triplicate (or quadruplicate, ...) numbers don't start separate sequences of their own.

The 4->1 really meaning that 4 is followed by another 4!

CountZero

"If you have four groups working on a compiler, you'll get a 4-pass compiler." - Conway's Law