Regex Tester & Validator

Matches lines beginning with the English articles 'The', 'A', or 'An'. The multiline flag makes the caret anchor apply at the start of every line rather than only the string beginning, while the global flag finds all occurrences. Commonly used for text processing tasks such as validating sentence openings, filtering article-led lines, or grammar analysis. Note the alternation order: a line starting with 'An' may match just 'A' first.