Regex Regular Expression
A compact language for finding and matching patterns in text.
\d+ = one or more digits. [A-Za-z] = a letter. ^https?:// = starts with http or https. Incredibly powerful; incredibly cryptic.
"Some people, when confronted with a problem, think 'I know, I'll use regular expressions.' Now they have two problems." — Jamie Zawinski. Use for simple things; avoid for complex parsing.