#!usr/bin/perl
use warnings;
use strict;


my $file =<<END;
object-group network HOSTNAME_1ST
 network-object host 10.1.1.1
 
object-group network HOSTNAME_2nd
 network-object host 10.3.1.1
 
object-group service WEB_TCP tcp
 port-object eq 80
END

my $hostname;

open my $fh, '<', \$file or die "unable to open read file $!";
while (my $line = <$fh>)
{
  if (my ($name) = $line =~ /^object-group network (\w+)/)
  {
     $hostname = $name; # "last seen hostname"
  }
  
  my ($ip) = $line =~ /(\d+\.\d+\.\d+\.\d+)/;
  
  if (defined ($ip) and $ip eq '10.3.1.1')
  {
     print "ip $ip goes with host name $hostname\n";  
  }
}
__END__
ip 10.3.1.1 goes with host name HOSTNAME_2nd