There seem to be many problems with the function of finding regular expressions.
(1) Expression: ([a-z]\1) Text: "a1 aa"
The matching result is "a1", but the actual correct value should be "aa".
(2) Expression: (ss?) Text: "ss s"
The expected behavior should be the first search for ss of range [1,2],
The second search for s of range [2,2]
The second search for s of range [4,4]
But there is actually no result of the second search.