exten => s,5,BackGround,blabla
Also, characters special to variable substitution, expression evaluation, etc (see below), can be quoted. For example, to literally use a $ on the string "$1231", quote it with a preceding \. Special characters that must be quoted to be used, are [ ] $ " \. (to write \itself, use \).
These Double quotes and escapes are evaluated at the level of the asterisk config file parser.
Double quotes can also be used inside expressions, as discussed below.