use strict;
my $str = '
Domain: myDomain.int
DNS: myDomain.int
Registered: 2013-05-17
Expires: 2023-05-31
Registration period: 1 year
VID: no
DNSSEC: Unsigned delegation, DNSSEC disabled, no records
Status: Active
Registrant
Handle: ***N/A***
Name: myName Corp
Attention: Reggie Person
Address: SomeStreet 17
Postalcode: numericZip
City: myCity
Country: XX
Phone: +12 34 56 78 90
Nameservers
Hostname: ns1.dom.ext
Hostname: ns2.dom.ext
Hostname: ns3.dom.ext
';
my $regex = qr/(?:Nameservers[^\n]*\n.*?)*(?>Hostname:\s+([\S]+)\n)/sp;
my $subst = '### push(@nameservers, $1); <-- it works :)\\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