From my notes when I did this:
CodePassing variables to KAREL program from URL: http://localhost/KAREL/URL_PARAM_TEST?chVar1="Hello"&chVar2="World" variables must be strings. chVar1 and chVar2 had to be decl'd in the KAREL file as String variables, with those exact names. The '?' is the separator between program name and variable list, '&' is separator between variables. Max 10 variables. URL_PARAM_TEST is KAREL program name. Replace "localhost" with robot IP address.
Thanks work perfectly. Also with relative path from /KAREL