Test, validate and match regular expressions
Matches 12-hour clock times in formats like '07:30 a.m.', '10:15 PM', or '9:45 A.M.'. It captures one or two digit hours, a colon, exactly two digit minutes, optional whitespace, and an AM/PM indicator with case-insensitive letters and optional periods. Commonly used for validating or extracting time strings from text where flexible period notation is needed.