RegExr: Online Regular Expression Testing Tool
bew*
b[A-Z0-9._%+-]+@[A-Z0-9.-]+.[A-Z]{2,4}b is a more complex pattern. It describes a series of letters, digits, dots, underscores, percentage signs and hyphens, followed by an at sign, followed by another series of letters, digits and hyphens, finally followed by a single dot and between two and four letters. In other words: this pattern describes an email address.