#23456789_123456789_123456789_123456789_123456789_123456789_123456789_
$_=<DATA>;push@_,@+while/_/g;{for$a(0..$#_){substr($_,$_[$a]-1,1
)=$;,$|++if($;=@{[/$a/g]})!=substr$_,$_[$a]-1,1}$|--&&redo}print

__DATA__
The number of 0s in this sentence is _, of 1s is _, of 2s is _, of 3s is _, of 4
s is _, of 5s is _, of 6s is _, of 7s is _, of 8s is _, and of 9s is _.