You are still assuming that a unique mapping is possible, but it isn't.
I investigated a little about what symbols and numbers people use to substitute to alphabetic characters, and I had this table:
As you can see, a single letter can map to three characters, and a single symbol can map to many characters...
A solution could be a junction, but we are speaking about Perl 5, and junctions will come with Perl 6... Any Perl 5 solution of this problem?
The very nature of Perl to be like natural language--inconsistant and full of dwim and special cases--makes it impossible to know it all without simply memorizing the documentation (which is not complete or totally correct anyway).
--John M. Dlugosz