Build, test, and debug regular expressions
Matches YouTube URL prefixes, including optional protocol (http/https), optional 'www.' subdomain, and both 'youtu.be' and 'youtube' domain forms, optionally followed by '.com/watch?v=' and a trailing slash. Commonly used to detect or extract YouTube links in text content. Note it matches the URL structure up to the query parameter but does not capture the actual video ID itself.