re = /^(([^<>()\[\]\.,;:\s@\"]+(\.[^<>()\[\]\.,;:\s@\"]+)*)|(\".+\"))@(([^<>()[\]\.,;:\s@\"]+\.)+[^<>()[\]\.,;:\s@\"]{2,})/im
str = 'prettyandsimple@example.com
very.common@example.com
disposable.style.email.with+symbol@example.com
other.email-with-dash@example.com
x@example.com (one-letter local part)
"much.more unusual"@example.com
"very.unusual.@.unusual.com"@example.com
"very.(),:;<>[]\\".VERY.\\"very@\\\\ \\"very\\".unusual"@strange.example.com
example-indeed@strange-example.com
admin@mailserver1 (local domain name with no TLD)
#!$%&\'*+-/=?^_`{}|~@example.org
"()<>[]:,;@\\\\\\"!#$%&\'*+-/=?^_`{}| ~.a"@example.org
" "@example.org (space between the quotes)
example@localhost (sent from localhost)
example@s.solutions (see the List of Internet top-level domains)
user@com
user@localserver
user@[IPv6:2001:db8::1]
©other.email-with-dash@example.com
?prettyandsimple@example.com
Invalid email addresses[edit]
Abc.example.com (no @ character)
A@b@c@example.com (only one @ is allowed outside quotation marks)
a"b(c)d,e:f;g<h>i[j\\k]l@example.com (none of the special characters in this local part are allowed outside quotation marks)
just"not"right@example.com (quoted strings must be dot separated or the only element making up the local part)
this is"not\\allowed@example.com (spaces, quotes, and backslashes may only exist when within quoted strings and preceded by a backslash)
this\\ still\\"not\\\\allowed@example.com (even if escaped (preceded by a backslash), spaces, quotes, and backslashes must still be contained by quotes)
john..doe@example.com (double dot before @)
with caveat: Gmail lets this through, Email address#Local-part the dots altogether
john.doe@example..com (double dot after @)'
subst = 'QuestionText = "$1",'
result = str.gsub(re, subst)
# Print the result of the substitution
puts result
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Ruby, please visit: http://ruby-doc.org/core-2.2.0/Regexp.html