c:\@Work\Perl\monks>perl -wMstrict -le
"use 5.010;
 ;;
 use Test::More 'no_plan';
 use Test::NoWarnings;
 ;;
 use Regexp::Common qw(net);
 ;;
 my $rx_IPv4_dd = qr{ (?<! \d) $RE{net}{IPv4} (?! \d) }xms;
 my $rx_arrow   = qr{ \s+ < \s+ }xms;
 ;;
 VECTOR:
 for my $ar_vector (
   'all these contain one or more IPv4 addresses',
   [ 'x (209.85.208.68) x (172.217.194.27 < 123.23.34.45) x',
     '209.85.208.68', '172.217.194.27', '123.23.34.45',
     ],
   [ ' < 209.85.208.68) x (172.217.194.27 < 123.23.34.45) x',
     '172.217.194.27', '123.23.34.45',
     ],
   [ 'x (1.2.3.4) x (9.8.7.6 < 5.6.7.8) x',
     '1.2.3.4', '9.8.7.6', '5.6.7.8',
     ],
   'none of these should match',
   [ '', ],  [ 'x', ],  [ '123', ],
   [ '209.85.208.68 (999.12.23.999) (12.23.34.45 98.76.54.32)', ],
   ) {
   if (not ref $ar_vector) {
     note $ar_vector;
     next VECTOR;
     }
   ;;
   my ($str, @expected) = @$ar_vector;
   ;;
   my @got = $str =~ m{
     (?|
       (?: [(] ($rx_IPv4_dd) (?= (?: $rx_arrow $rx_IPv4_dd)? [)] ) )
       |
       (?: \G (?! \A) $rx_arrow ($rx_IPv4_dd) [)] )
     )
     }xmsg;
   is_deeply \@got, \@expected, qq{'$str' -> (@expected)};
   }
 ;;
 done_testing;
 ;;
 exit;
"
# all these contain one or more IPv4 addresses
ok 1 - 'x (209.85.208.68) x (172.217.194.27 < 123.23.34.45) x' -> (209.85.208.68 172.217.194.27 123.23.34.45)
ok 2 - ' < 209.85.208.68) x (172.217.194.27 < 123.23.34.45) x' -> (172.217.194.27 123.23.34.45)
ok 3 - 'x (1.2.3.4) x (9.8.7.6 < 5.6.7.8) x' -> (1.2.3.4 9.8.7.6 5.6.7.8)
# none of these should match
ok 4 - '' -> ()
ok 5 - 'x' -> ()
ok 6 - '123' -> ()
ok 7 - '209.85.208.68 (999.12.23.999) (12.23.34.45 98.76.54.32)' -> ()
1..7
ok 8 - no warnings
1..8