The caret means that we're going to use this expression to examine a string starting at the string's beginning.
The expression whatever the previous item was that we're checking on.
In this case, an email address must start with one or more of any combination of the characters "a" through "z", "A" through "Z", "0" through "9", or underscore. Because of the brackets, the entered string can have either a period or a dash here, but not both.
A regular expression can be a single character, or a more complicated pattern.
Regular expressions can be used to perform all types of text search and text replace operations.
Suggestion's if the regex is correct: Wiki Link Local_part The local-part of the email address may use any of these ASCII characters. RFC 6531 permits Unicode characters beyond the ASCII range: .