As selective, less verbose, non-repetitive, more readable, better IMHO:

    my $octet_dec = qr{ [01]?\d\d? | 2[0-4]\d | 25[0-5] }xms;

    my $ipv4_dec = qr{ $octet_dec (?: [.] $octet_dec){3} }xms;

Update: Or better yet, as already mentioned, Regexp::Common::net.