@ISXDIGIT[string]: Returns 1 if string is entirely composed of hexadecimal digits (0- 9,A-F, a-f); 0 otherwise.
See also: @ISALNUM, @ISALPHA, @ISASCII, @ISCNTRL, @ISDIGIT, @ISPRINT, @ISPUNCT, @ISSPACE.
Example:
echo %@isxdigit[0]
0
echo %@isxdigit[7F]
1
echo %@isxdigit[0x7F]
1