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'
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