Regex
Online regex live
What is Unicode and UTF-8 and UTF-16 encoding ?
Unicode exaplained Stack Overflow CEO
Unicode SO
Utf-8 encoding
Unicode youtube
What is word boundary SO
Catastrophic Backtracking
Convert from regex to NFA to DFA
By default python3 is unicode enabled.
By default all the quantifiers *, +, ? work in greedy mode.
.(dot) is wildcard.