정규표현식

http://zvon.org/comp/r/tut-Regexp.html

https://www.youtube.com/watch?v=V_ePeBaQzSc&list=PLB9NsRTifc1nc8J5BJhkE3AP9oieECVpJ&index=1

https://regexr.com/

(gskinner.com/regexr/)