use strict;
my $str = 'Nmap scan report for 192.168.0.21
Host is up (0.18s latency).
Not shown: 1 filtered port
Some closed ports may be reported as filtered due to --defeat-rst-ratelimit
PORT STATE SERVICE
22/tcp open ssh
Nmap scan report for 192.168.0.29
Host is up (0.029s latency).
Not shown: 1 filtered port
Some closed ports may be reported as filtered due to --defeat-rst-ratelimit
PORT STATE SERVICE
22/tcp open ssh
Nmap scan report for 192.168.0.25
Host is up (0.15s latency).
Not shown: 1 filtered port
Some closed ports may be reported as filtered due to --defeat-rst-ratelimit
PORT STATE SERVICE
22/tcp open ssh';
my $regex = qr/(?s).*?(\z|\d+\.\d+\.\d+\.\d+)/mp;
my $subst = '$1\\n';
my $result = $str =~ s/$regex/$subst/rg;
print "The result of the substitution is' $result\n";
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Perl, please visit: http://perldoc.perl.org/perlre.html