re =/(?<addr_spec> \g<local_part> @ \g<domain> ){0}
(?<local_part> \g<dot_atom> | \g<quoted_string> | \g<obs_local_part> ){0}
(?<domain> \g<dot_atom> | \g<domain_literal> | \g<obs_domain> ){0}
(?<domain_literal> \g<CFWS>? \[ (?: \g<FWS>? \g<dtext> )* \g<FWS>? \] \g<CFWS>? ){0}
(?<dtext> [\x21-\x5a] | [\x5e-\x7e] | \g<obs_dtext> ){0}
(?<quoted_pair> \\ (?: \g<VCHAR> | \g<WSP> ) | \g<obs_qp> ){0}
(?<dot_atom> \g<CFWS>? \g<dot_atom_text> \g<CFWS>? ){0}
(?<dot_atom_text> \g<atext> (?: \. \g<atext> )* ){0}
(?<atext> [a-zA-Z0-9!#$%&'*+\/=?^_`{|}~-]+ ){0}
(?<atom> \g<CFWS>? \g<atext> \g<CFWS>? ){0}
(?<word> \g<atom> | \g<quoted_string> ){0}
(?<quoted_string> \g<CFWS>? " (?: \g<FWS>? \g<qcontent> )* \g<FWS>? " \g<CFWS>? ){0}
(?<qcontent> \g<qtext> | \g<quoted_pair> ){0}
(?<qtext> \x21 | [\x23-\x5b] | [\x5d-\x7e] | \g<obs_qtext> ){0}
# comments and whitespace
(?<FWS> (?: \g<WSP>* \r\n )? \g<WSP>+ | \g<obs_FWS> ){0}
(?<CFWS> (?: \g<FWS>? \g<comment> )+ \g<FWS>? | \g<FWS> ){0}
(?<comment> \( (?: \g<FWS>? \g<ccontent> )* \g<FWS>? \) ){0}
(?<ccontent> \g<ctext> | \g<quoted_pair> | \g<comment> ){0}
(?<ctext> [\x21-\x27] | [\x2a-\x5b] | [\x5d-\x7e] | \g<obs_ctext> ){0}
# obsolete tokens
(?<obs_domain> \g<atom> (?: \. \g<atom> )* ){0}
(?<obs_local_part> \g<word> (?: \. \g<word> )* ){0}
(?<obs_dtext> \g<obs_NO_WS_CTL> | \g<quoted_pair> ){0}
(?<obs_qp> \\ (?: \x00 | \g<obs_NO_WS_CTL> | \n | \r ) ){0}
(?<obs_FWS> \g<WSP>+ (?: \r\n \g<WSP>+ )* ){0}
(?<obs_ctext> \g<obs_NO_WS_CTL> ){0}
(?<obs_qtext> \g<obs_NO_WS_CTL> ){0}
(?<obs_NO_WS_CTL> [\x01-\x08] | \x0b | \x0c | [\x0e-\x1f] | \x7f ){0}
# character class definitions
(?<VCHAR> [\x21-\x7E] ){0}
(?<WSP> [ \t] ){0}
^\g<addr_spec>$/x
 
p re.match?('+1~1+@iana.org')
p re.match?('test@[123.123.123.123')

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