(root)/
libxml2-2.12.3/
test/
regexp/
ranges2
=>(a|b{0,3}){0,1}
a
aa
b
bb
bbb
bbbb
ab
ba
=>([0-9]{0,3}|([0-9]{0}|[0-9]{0,3})){0,3}
0
00
123
abc