+let regexp paren = [ '(' '[' '{' ')' ']' '}' ]
+let regexp implicit = '?'
+let regexp symbol_char =
+ [^ 'a' - 'z' 'A' - 'Z' '0' - '9'
+ ' ' '\t' '\n'
+ '\\' '(' '[' '{' ')' ']' '}' '?'
+ ]
+let regexp comment_char = [^ '\n' ]
+let regexp comment = "%%" comment_char*