+
+my $rfc822re;
+
+sub make_rfc822re {
+# Basic lexical tokens are specials, domain_literal, quoted_string, atom, and
+# comment. We must allow for rfc822_lwsp (or comments) after each of these.
+# This regexp will only work on addresses which have had comments stripped
+# and replaced with rfc822_lwsp.
+
+ my $specials = '()<>@,;:\\\\".\\[\\]';
+ my $controls = '\\000-\\037\\177';
+
+ my $dtext = "[^\\[\\]\\r\\\\]";
+ my $domain_literal = "\\[(?:$dtext|\\\\.)*\\]$rfc822_lwsp*";
+
+ my $quoted_string = "\"(?:[^\\\"\\r\\\\]|\\\\.|$rfc822_lwsp)*\"$rfc822_lwsp*";
+
+# Use zero-width assertion to spot the limit of an atom. A simple
+# $rfc822_lwsp* causes the regexp engine to hang occasionally.
+ my $atom = "[^$specials $controls]+(?:$rfc822_lwsp+|\\Z|(?=[\\[\"$specials]))";
+ my $word = "(?:$atom|$quoted_string)";
+ my $localpart = "$word(?:\\.$rfc822_lwsp*$word)*";
+
+ my $sub_domain = "(?:$atom|$domain_literal)";
+ my $domain = "$sub_domain(?:\\.$rfc822_lwsp*$sub_domain)*";
+
+ my $addr_spec = "$localpart\@$rfc822_lwsp*$domain";
+
+ my $phrase = "$word*";
+ my $route = "(?:\@$domain(?:,\@$rfc822_lwsp*$domain)*:$rfc822_lwsp*)";
+ my $route_addr = "\\<$rfc822_lwsp*$route?$addr_spec\\>$rfc822_lwsp*";
+ my $mailbox = "(?:$addr_spec|$phrase$route_addr)";
+
+ my $group = "$phrase:$rfc822_lwsp*(?:$mailbox(?:,\\s*$mailbox)*)?;\\s*";
+ my $address = "(?:$mailbox|$group)";
+
+ return "$rfc822_lwsp*$address";
+}
+
+sub rfc822_strip_comments {
+ my $s = shift;
+# Recursively remove comments, and replace with a single space. The simpler
+# regexps in the Email Addressing FAQ are imperfect - they will miss escaped
+# chars in atoms, for example.
+
+ while ($s =~ s/^((?:[^"\\]|\\.)*
+ (?:"(?:[^"\\]|\\.)*"(?:[^"\\]|\\.)*)*)
+ \((?:[^()\\]|\\.)*\)/$1 /osx) {}
+ return $s;
+}
+
+# valid: returns true if the parameter is an RFC822 valid address
+#
+sub rfc822_valid {
+ my $s = rfc822_strip_comments(shift);
+
+ if (!$rfc822re) {
+ $rfc822re = make_rfc822re();
+ }
+
+ return $s =~ m/^$rfc822re$/so && $s =~ m/^$rfc822_char*$/;
+}
+
+# validlist: In scalar context, returns true if the parameter is an RFC822
+# valid list of addresses.
+#
+# In list context, returns an empty list on failure (an invalid
+# address was found); otherwise a list whose first element is the
+# number of addresses found and whose remaining elements are the
+# addresses. This is needed to disambiguate failure (invalid)
+# from success with no addresses found, because an empty string is
+# a valid list.
+
+sub rfc822_validlist {
+ my $s = rfc822_strip_comments(shift);
+
+ if (!$rfc822re) {
+ $rfc822re = make_rfc822re();
+ }
+ # * null list items are valid according to the RFC
+ # * the '1' business is to aid in distinguishing failure from no results
+
+ my @r;
+ if ($s =~ m/^(?:$rfc822re)?(?:,(?:$rfc822re)?)*$/so &&
+ $s =~ m/^$rfc822_char*$/) {
+ while ($s =~ m/(?:^|,$rfc822_lwsp*)($rfc822re)/gos) {
+ push(@r, $1);
+ }
+ return wantarray ? (scalar(@r), @r) : 1;
+ }
+ return wantarray ? () : 0;
+}