rewrote @operator .. @on .. syntax to expr > expr > expr
made left recursion enabled optional (-l to disable flag, or allowLeftRecursion as parser option)
added a lot of left recursion test cases
fixed case where left recursion could lead to unendless looping
Implemented default labels (::)
Implemented default labels (::)
removed superfluous input detection, since 'expected <nothing>' basically expresses the same