I have been using regular expressions quite liberally since I learned how to write them. I haven’t really made any very complex ones at all. Until I decided to make one that would validate e-mail addresses. I first downloaded the RFC822 and RFC2822. These are the documents that actually outline the format of e-mail messages. I also grabbed the RFC1035 which describes the domain name service formats for the Internet , to make sure that domain part of an e-mail follows its more strict rules.

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