"example_rexps":- <a_star> ::= $ | a+ -- = a*, zero or more as <a_plus> ::= aa* -- = a+, one or more as <a_quest> ::= $ | a -- = a?, zero or one as <a_3> ::= a{3} -- = aaa, three as <a_3_5> ::= a{3,5} -- = a{3}a?a? <a_3_> ::= a{3,} -- = a{3}a* "example_sets":- <lls> ::= a-z -- little letters <not_lls> ::= ~a-z -- anything but little letters <ls_ds> ::= [a-zA-Z0-9] -- letters and digits <sym> ::= `!@@#$' -- the symbols !, @@, # and $ <sym_q_nl> ::= [`!#@@$'^'^n] -- the above symbols with ' and newline <quotable> ::= ^p#^' -- any graphic character except ' <del> ::= ^127 -- ASCII DEL