I would like to munge regex strings to interpolate substrings in them (I know you can do that in CL-PPCRE using the SEXP based regexps).

Something equivalent

(defvar L "[A-Za-z]")

(scan #?"|${L}+|" " |foobar|...")

But I would like to build the interpolated string dynamically, i.e., *before* I create the L variable. In other words, I would like to interpolate at the latest possible time.

I know I am doing something wrong.

Thanks

Marco