Regexp#match? should be considered to be part of the Ruby core library. We are
emulating it for < 2.4, but not having to require the extension is part of the
illusion of the emulation.
In Ruby ^ and $ mean start and end of *line*.
A regexp that validates an email should not check if
some line of the string looks like an email, and maybe
be surrounded by the entire Joyce's Ulysses. What the
regexp has to check is if the string itself looks like
an email.
This validator is used only in tests, the ^/$ anchors
implied no risk.
