#!/usr/bin/perl

my (%data); # the hash
my ( @an_array);  # array
$count=15;

open HOSTS,"/etc/hosts";
while( <HOSTS> ) {
   chomp;
   if ( ! /^#/  &&  ! /^\s*$/ ){
	   ($ip1, $ip2,$ip3 ,$remain ) = split /\./ ;
	    ( $ip4, $hostname ) = split( /\s+/, $remain ); 
	   $info=sprintf "<%3s> <%3s> <%3s> <%3s>", $ip1,$ip2,$ip3,$ip4   ;
	   $data{$hostname} = $info;
   }
};

foreach  $name ( sort(  keys(%data)  )  ){
   printf "%2d  %s  .. %s\n",$count--, $data{ $name }, $name ;
 
}
print "__________________\n";

while( <> ){
	chomp;
	if ( defined $data{ $_ } ){
		printf "%2d  %s  .. %s\n",$count--, $data{ $_ }, $_ ;
	}else{
		printf "the host '%s' does not exist \n",$_
	}
}