Regex Tester & Validator

Matches any line ending with the literal domain '@up-sider.com', optionally followed by a trailing forward slash before the line's end. The multiline flag makes the $ anchor match at the end of each line rather than the end of the string, while the global flag finds all occurrences. Commonly used to filter or validate email addresses from the up-sider.com domain, including cases where a stray slash appears (e.g., in URL-embedded emails). Note that the escaped slash (\/) is unnecessary in most contexts outside JavaScript-style /.../ delimiters.