Looks like a broken attempt at parsing an e-mail address. Broken because:

• Not just any character can be part of an e-mail address (though there are more characters allowed than most people think).
• Domain names don't necessarilly have a dot in them.
• More then one '@' character is allowed in an e-mail address to specify a relay. The regex you have would match it, but wouldn't get the correct user (the greediness of + would put the relay as part of the user portion). (To be fair, this syntax is usually disallowed due to the spammer-friendly nature of this mis-feature).

The accepted regex for parsing an e-mail address is several hundred characters long, and it doesn't even match embedded comments. See Email::Valid.