Regex Tester & Validator

This regular expression matches entire lines that consist of a lowercase letter followed by zero or more word characters (letters, digits, or underscores). With the multiline flag, it verifies each line independently, making it useful for validating simple identifiers, variable names, or tokens that must start with a lowercase letter and contain only alphanumeric characters and underscores. It is commonly applied in form validation, syntax checking, and text preprocessing.