Regex Tester & Validator

This regex matches C++ file stream open calls such as `myfile.open("data.txt")`. It uses two named capture groups: "first_part" captures the stream object name and the `.open(` call, while "file_name" captures the quoted filename string containing alphanumeric characters, underscores, and dots. It's useful for parsing, validating, or refactoring C++ code that uses ifstream/ofstream to open files. Note the character range A-z unintentionally includes some punctuation like brackets and backslash.