The any statement will match any character that is in the store snStore. This statement is only valid on the left side of a rule; the index statement is used to match again or output the character matched by the any statement in the output. If an any is used in the key, it will be expanded out to include one rule for each character in the store. The any statement remembers the offset in the store where the match for later use with the index statement.
+ any(keys) > index(output,1)