Regexp::Common (with the automatically loaded Regexp::Common::net) can simplify IP extraction. For one thing, it (Update: can be used to create a regex that) will not match IPs with invalid (Update: decimal) octets such as are allowed by [0-9]{1,3} (try different invalid octets in the $s string).
>perl -wMstrict -le
"use Regexp::Common qw(net);
;;
my $s = 'host1 dns:192.168.243.30,asdf';
my $IP = qr{ (?<! \d) $RE{net}{IPv4} (?! \d) }xms;
my ($ip) = $s =~ m{ $IP }xmsg;
print qq{ip '$ip'} if $ip;
"
ip '192.168.243.30'