Normally I would have said: Do what ASerge says and add '$' to the set "Digits' in fpexprpars (immediately after "implementation").
But the parser still fails. The problem is in the line "val(FToken,X,I)" of TFPExpressionScanner.IsNumber, where FToken is the number string with the $, e.g. '$10'.
If I call "val('$10', X, I)" by itself it is converting the hex number without an issue, but inside fpexprpars it fails. What's going on here?
See attached project (it contains already a patched recent fpexprpars).