^(How To|What is).\*
This regular expression will match any string that starts with "How To" or "What is", in any combination of upper and lower case letters. The "^" symbol indicates the start of the string, and the "(How To|What is)" portion matches either "How To" or "What is". The ".\*" portion matches any character (including spaces) zero or more times, ensuring that the rest of the string will be matched as well.
Note that this regular expression uses RE2 syntax, which does not support certain features such as lookaheads and backreferences. It is optimized for performance and security, and is generally recommended for use in production systems.
