不考虑符号，匹配5位回文字符串

Question

five letter palindromes(words that are the same backwards as forwards)(kayak,dewed,eye,refer)

这一题有点没有头绪。不知道怎么写啊

Answer 1

^([a-zA-Z])([a-zA-Z])[a-zA-Z]\2\1$用\1、\2引用前面匹配到的字符。