allow forward slash in strings for if statements

src/variable.cpp

@@ -4902,7 +4902,7 @@ double Variable::evaluate_boolean(char *str)
       // set I to end of string
 
       int istart = i++;
-      while (isalnum(str[i]) || str[i] == '_') i++;
+      while (isalnum(str[i]) || (str[i] == '_') || (str[i] == '/')) i++;
 
       int n = i - istart + 1;
       argstack[nargstack].str = new char[n];