TeX Puzzle: Counting tokens in a given token list in an expandable way

bxtllength.sty

^^5cdef^^5c^^6ce^^6e^^67^^74^^68^^7b^^5c^^78^^78^^40^^6ce^^6e^^40^^69^^6e^^69^^7d
^^5cdef^^5c^^78^^78^^40^^71^^40^^6dc^^7b^^5c^^6e^^6fe^^78^^70a^^6ed^^5c^^78^^78^^40^^71^^40^^6dc^^40^^7d
^^5cdef^^5c^^78^^78^^40^^71^^40^^6d^^6b^^7b^^5c^^6e^^6fe^^78^^70a^^6ed^^5c^^78^^78^^40^^71^^40^^6d^^6b^^40^^7d
^^5cdef^^5c^^78^^78^^40ca^^72^^231^^232^^7b^^231^^7d
^^5cdef^^5c^^78^^78^^40cd^^72^^231^^232^^7b^^232^^7d
^^5cdef^^5c^^78^^78^^40^^67b^^6c^^231^^7b^^7d
^^5cdef^^5c^^78^^78^^40^^6d^^74^^7b^^7d
^^5cdef^^5c^^78^^78^^40^^69f^^78^^231^^7b^^5c^^69f^^78^^231\expandafter^^5c^^78^^78^^40ca^^72^^5ce^^6c^^73e\expandafter^^5c^^78^^78^^40cd^^72^^5cf^^69^^7d
^^5cdef^^5c^^78^^78^^40^^69f^^6d^^74^^231^^7b^^5c^^78^^78^^40^^69f^^78^^7b^^5c^^78^^78^^40^^71^^40^^6dc^^231^^5c^^78^^78^^40^^71^^40^^6dc^^7d^^7d
^^5cdef^^5c^^78^^78^^40^^6ce^^6e^^40^^69^^6e^^69^^231^^7b^^5c^^78^^78^^40^^6ce^^6e^^7b^^231^^7b^^5c^^78^^78^^40^^6d^^74^^7d^^7d^^7d
^^5cdef^^5c^^78^^78^^40^^6ce^^6e^^231^^7b^^5c^^78^^78^^40^^6ce^^6e^^40a^^231^^5c^^78^^78^^40^^71^^40ea^^5c^^78^^78^^40^^71^^40eb^^7d
^^5cdef^^5c^^78^^78^^40^^6ce^^6e^^40a^^231^^23^^7b^^5c^^78^^78^^40^^6ce^^6e^^40^^70^^68^^7b^^231^^7d^^5c^^78^^78^^40^^6ce^^6e^^40b^^7d
^^5cdef^^5c^^78^^78^^40^^6ce^^6e^^40b^^231^^232^^5c^^78^^78^^40^^71^^40eb^^7b^^5c^^78^^78^^40^^6ce^^6e^^40c^^7b^^231^^7d^^232^^232^^7d
^^5cdef^^5c^^78^^78^^40^^6ce^^6e^^40c^^231^^232^^5c^^78^^78^^40^^71^^40ea^^7b^^5c^^78^^78^^40^^69f^^6d^^74^^7b^^232^^7d^^7b^^5c^^78^^78^^40^^6ce^^6e^^40f^^69^^6e^^7d^^7b^^5c^^78^^78^^40^^6ce^^6e^^40d^^7b^^231^^7d^^5c^^78^^78^^40^^71^^40eb^^7d^^7d
^^5cdef^^5c^^78^^78^^40^^6ce^^6e^^40d^^231^^232^^5c^^78^^78^^40^^71^^40ea^^7b^^5c^^78^^78^^40^^6ce^^6e^^40^^67^^72^^7b^^231^^7d^^5c^^78^^78^^40^^6ce^^6e^^40e^^7b^^232^^7d^^7d
^^5cdef^^5c^^78^^78^^40^^6ce^^6e^^40e^^231^^7b\expandafter^^5c^^78^^78^^40^^6ce^^6e\expandafter^^7b^^5c^^78^^78^^40^^67b^^6c^^231^^7d^^7d
^^5cdef^^5c^^78^^78^^40^^6ce^^6e^^40f^^69^^6e^^231^^5c^^78^^78^^40^^71^^40ea^^7b^^7d
^^5cdef^^5c^^78^^78^^40^^6ce^^6e^^40^^67^^72^^7b^^5c^^78^^78^^40c^^6f^^75^^6e^^74^^5c^^78^^78^^40c^^6f^^75^^6e^^74^^5c^^78^^78^^40^^6ce^^6e^^40^^69^^6e^^69^^7d
^^5cdef^^5c^^78^^78^^40^^6ee^^78^^74^^231^^7b^^25
^^5cdef^^5c^^78^^78^^40^^6ce^^6e^^40^^70^^68^^23^^231^^7b^^5c^^78^^78^^40^^6ce^^6e^^40^^70^^68^^40a^^7b^^23^^231^^231^^7d^^7d^^25
^^5cdef^^5c^^78^^78^^40^^6ce^^6e^^40^^70^^68^^40a^^23^^231^^7b^^5c^^78^^78^^40^^6ce^^6e^^40^^70^^68^^40b^^23^^231^^5c^^78^^78^^40^^71^^40ec^^7d^^25
^^5cdef^^5c^^78^^78^^40^^6ce^^6e^^40^^70^^68^^40b^^23^^231^^231^^23^^232^^5c^^78^^78^^40^^71^^40ec^^7b^^5c^^78^^78^^40^^6ce^^6e^^40c^^6c^^7b^^23^^231^^7d^^5c^^78^^78^^40^^6ce^^6e^^40^^70^^68^^40c^^7b^^23^^232^^7d^^7d^^25
^^5cdef^^5c^^78^^78^^40^^6ce^^6e^^40^^70^^68^^40c^^23^^231^^7b^^5c^^78^^78^^40^^69f^^6d^^74^^7b^^23^^231^^7d^^7b^^7d^^7b^^5c^^78^^78^^40c^^6f^^75^^6e^^74^^5c^^78^^78^^40^^6ce^^6e^^40^^70^^68^^40a^^7b^^23^^231^^7d^^7d^^7d^^25
^^7d^^5c^^78^^78^^40^^6ee^^78^^74^^7b^^20^^7d
^^5cdef^^5c^^78^^78^^40^^6ce^^6e^^40c^^6c^^231^^7b^^5c^^78^^78^^40^^6ce^^6e^^40c^^6c^^40a^^231^^5c^^78^^78^^40^^71^^40^^6d^^6b^^7d
^^5cdef^^5c^^78^^78^^40^^6ce^^6e^^40c^^6c^^40a^^231^^7b^^5c^^78^^78^^40^^69f^^78^^7b^^231^^5c^^78^^78^^40^^71^^40^^6d^^6b^^7d^^7b^^7d^^7b^^5c^^78^^78^^40c^^6f^^75^^6e^^74^^5c^^78^^78^^40^^6ce^^6e^^40c^^6c^^40a^^7d^^7d
^^5cdef^^5c^^78^^78^^40c^^6f^^75^^6e^^74^^7b^^2a^^7d

test-bxtllength.tex

% \length{<tl>} must full-expand to a token list that consists of
% as many '*' as the number of tokens in <tl>.
\documentclass{article}
\usepackage{bxtllength}
\edef\result{\length{ \a {b\cd ef{g} }\h }}% has 13 tokens
\show\result %==>*************
\edef\result{\length{{ }{ {}} {}}}% has 11 tokens
\show\result %==>***********
\begin{document}
\end{document}

The code in bxtllength.sty is obfuscated, since it contains the solution to the puzzle.