@TALNUM[string]: Returns the number of alphabetic (a-z, A-Z) and/or numeric (0 - 9) characters in string.
See also: @TALPHA, @TASCII, @TCNTRL, @TDIGIT, @TLOWER, @TPRINT, @TPUNCT, @TSPACE, @TUPPER, and @TXDIGIT.
Example:
echo %@talnum[123abc]
6
echo %@talnum[123 abc]
6
echo %@talnum[1-2-3]
3