I've done something similar in my cfperl program, which parses cfengine rules that look like this (a AND b OR c):

a.b|c

I use Parse::RecDescent to turn text input directly into a parsed optree, which is then interpreted at runtime because parts of the tree change value depending on what's defined at the time. You can probably do the same with prefix instead of infix notation - the grammar changes are minor.

HTH

Ted