>perl -wMstrict -le
"my $decimal_octet =
   qr{ 2 (?: [0-4] \d | 5 [0-5]) | [01]? \d? \d }xms;
 my $ip =
   qr{ (?<! \d) $decimal_octet (?: \. $decimal_octet){3} (?! \d) }xms;
 print $ip;
 ;;
 my $s = '123.45.6.234 xx yyy zz 000.12.34.255';
 my @ips = $s =~ m{ $ip }xmsg;
 printf qq{'$_' } for @ips;
"
(?^msx: (?<! \d) (?^msx: 2 (?: [0-4] \d | 5 [0-5]) | [01]? \d? \d ) (?: \. (?^msx: 2 (?: [0-4] \d |
5 [0-5]) | [01]? \d? \d )){3} (?! \d) )
'123.45.6.234' '000.12.34.255'