def is_a_valid_email?(email)
  (email =~ /^(([A-Za-z0-9]*.+*_+)|([A-Za-z0-9]+-+)|([A-Za-z0-9]++)|([A-Za-z0-9]++))*[A-Z‌​a-z0-9]+@{1}((w+-+)|(w+.))*w{1,63}.[a-zA-Z]{2,4}$/i)
end

hello.me_1@email.com # <~~ valid
foo.bar#gmail.co.uk # <~~~valid
f.o.o.b.a.r@gmail.com # <~~~valid
f...bar@gmail.com # <~~ not valid
get_at_m.e@gmail  #<~~ valid

VALID_EMAIL_REGEX = /A[w+-.]+@[a-zd-]+(.[a-zd-]+)*.[a-z]+z/i

VALID_EMAIL_REGEX = /A[w+-.]+@[a-zd-]+(.[a-z]+)*.[a-z]+z/i

VALID_EMAIL_REGEX = /A([w+-].?)+@[a-zd-]+(.[a-z]+)*.[a-z]+z/i

VALID_EMAIL_REGEX = /A[w+-.]+@[a-zd-]+(.[a-zd-]+)*.[a-z]+z/i

`! $ & * - = ` ^ | ~ # % ' + / ? _ { }`

/A[^@s]+@[^@s]+z/

".....@a....",
  "david.gilbertson@SOME+THING-ODD!!.com",
  "a.b@example,com",
  "a.b@example,co.de"

VALID_EMAIL_REGEX = /A[w+-.]+@[a-zd-]+(.[a-zd-]+)*.[a-z]+z/i

> 'some@email.with-subdomain.com' =~ VALID_EMAIL_REGEX
=> 0

if email.match?('[a-z0-9]+[_a-z0-9.-]*[a-z0-9]+@[a-z0-9-]+(.[a-z0-9-]+)*(.[a-z]{2,4})')
      puts 'matches!'
else
      puts 'it doesn't match!'
end

/A[a-zA-Z0-9.!#$%&'*+/=?^_`{|}~-]+@[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?(?:.[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?)*z/