Syntactic Sugar

Ex:

RegEx : /a+|[0-3]/
SRegEx: a.repeat(1-) | set(0-3)

A+ === AA* === A.repeat(1-) === AA.repeat(0-)
A? === A|ε === A.repeat(0-1)

[0-9] === 0|1|2|3|4|5|6|7|8|9 === set(0-9)