#!/usr/sup/gnu/bin/perl

# Definition pick more or less straight from RFC-822.
$atom = '[^()<>@,;:\".\[\] \000-\037\177]+';
$quoted = '"(?:[^"\\\n]|\\.)*"';
$word = "(?:$atom|$quoted)";
$localpart = "$word(?:\.$word)*";
$subdomain = "(?:$atom|\\[(?:[^\\[\\]\\\\\\r]|\\.)*\\])";
$domain = "$subdomain(?:\.$subdomain)*";
$addrspec = "$localpart\@$domain";
$route = "(?:\@$domain)+:";
$routeaddr = "<$route?$addrspec>";
$mailbox = "(?:$addrspec|$word+$routeaddr)";
$group = "$word+:(?:$mailbox(?:,+$mailbox)*)?;";
$address = "$mailbox|$group";

sub valid_address {
    local($_) = @_;
# Remove comments, remember that comments might nest.


    1 while s/\((?:[^()]|\\[()])*?[^\\]\)/ /g;
    /$address/o;
}

# Either read the arguments or read the standard input (line by line).
if (@ARGV > 0) { 
    foreach (@ARGV) {
	print "$_ is ", valid_address($_) ? "" : "not ", "valid\n";
    }
} else {
    while (<>) {
	chop;
	print "$_ is ", valid_address($_) ? "" : "not ", "valid\n";
    }
}