Splitting Ranges using Lambda Predicates

["Nordlöw" via Digitalmars-d-learn]

I'm missing a version of splitter that can be used to split 
ranges based on arbitrary predicates. I need to for conversion 
between different symbol casings, typically:

1. someName => SomeName

In this case the lambda should take two arguments (a,b)

where in

1. a should be lowercase and b should be uppercase

Have i missed a reusable component that can be applied here?