RULE-EXP := (CL:* RULE-EXP)
| (:LIST RULE-EXP RULE-EXP)
Rule expression (CL:+ RULE-EXP) is similar to CL:*, but matches 1 or
more repetitions of RULE EXP.
-(:MAYBE RULE-EXP) defines optional elements. If RULE-EXP doesn't
+(:MAYBE RULE-EXP+) defines optional elements. If RULE-EXP doesn't
match, NIL is returned as semantic value, otherwise semantic value of
+RULE-EXP is used (if there are several RULE-EXPs, list of their
+semantic values is returned).
(:LIST RULE-EXP1 RULE-EXP2) finds non-empty list of RULE-EXP1
delimited by RULE-EXP2. Semantic values aof RULE-EXP1 and RULE-EXP2