Build, test, and debug regular expressions
Matches Slack message metadata to strip when cleaning text copied from chat exports: lines with timestamps (colon plus digits like '5:00 PM'), lines containing 'replies', lines ending in a digit (reply counts), colon-only lines such as usernames ('James:'), 'Last reply' markers, and blank lines. With global and multiline flags, it removes each junk line along with its trailing newlines, leaving only the actual message content. Typically used in editors like VS Code with an empty-string replacement to sanitize pasted Slack conversations.