AutoCAD Visual LISP / AutoLISP :: STRNUM Error - No Function Definition

I D/L a lisp file (setvars.lsp) that purports to give a list of system variables that match a short string entered in a dialog box.

Unfortunately, an error arises that says 'error : no function definition: STRNUM'

I've looked at the code and can't tell what the writer was hoping to achieve.

The specific section is as follows:

    (if F1
      (progn
        (setq RL (read-line F1))
        (while RL
          (if (and (wcmatch (strcase RL) (strcase (strcat "*" DESCR1 "*")))
                   (wcmatch (strcase RL) (strcase (strcat "*" DESCR2 "*")))
[Code] .........

There is no other mention of STRNUM in the whole of the lisp.

There is an accompanying setvars.dat, wherein apparently, the writer compiled a data file of all the system variables in AutoCAD2008, each variable being followed by an '=' and then a description of the variable.

If necessary I can post the whole lisp and dat file, but was hoping to discover the intention from the above extract and therfore where I might work out an alternative to this line.

Looking to turn a string to a real? If so, why are there two 'arguments' following the 'function' STRNUM?