#!/usr/bin/perl 
######################################################################
#####################################################################
####################################################################
###################################################################
# Set Variable file modification
#****************************************************************
$datefile = `date '+%m%d%y'`;
# Copy current /etc/hosts file to the work directory (/etc/work/hostsf
+ile)
 
#*************************************************************
# Search and file section for hosts file entry

#Main Program
format STDOUT =
@>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
+>
"*********************************************************************
+"
@>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
"*******************************************************************"
@>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
"****************************************************************"

        @|||||||||||||||||||||||||||||||||||||||
        "ETC Hosts File Inplace Edit Program"
         @|||||||||||||||||||||||||||||||||||||||||||||||||||||
    "Inplace Edit (Work Directory: /etc/work/hostfiles)"

@>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
"****************************************************************"
@>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
"*******************************************************************"
@>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
+>>
"*********************************************************************
+*"

.
write;

########################### Main Program Section #####################
+###
print "\n"; 
print "This program is will copy the current etc/hosts file to the \n"
+;
print "working directory (/etc/work/hostfile) to perform the \"Inplace
+\,\"  \n";
print "edit of the new or modified directories. \n";
print "\n"; 
print "Should I continue with the process, or exit for another time? (
+Yes|No): ";
$choice1 = <STDIN>;
chomp($choice1);
while ($choice1 =~ m/No|NO|no|N|n/)
{
    print "Now exiting the program. \n";
    print "Please wait . . . .\n";
    `sleep 5`;
    exit;     
}
print "Please enter the following the following information . . .\n";
print "New System IP Address (Example - 10.12.13.14): ";
$NewIP = <STDIN>;
chomp($NewIP);
print "Absolute name of system or device (Example - neptune.itdo.pri):
+ ";
$NewLgName = <STDIN>;
chomp($NewLgName);
print "Short name of system or device (Example - neptune): ";
$NewStName = <STDIN>; 
chomp($NewStName);
######################## Array #######################################
+##
@input = ($NewIP, $NewLgName, $NewStName);
######################## Sub Routine Call Section ####################
+###
&copyFile;
&editPlace(*input);

########################### Sub Routine Section ######################
+###
sub copyFile
{
    `cp /etc/hosts /etc/work/hostfiles/hosts`;
    $TargetDir = "/etc/work/hostfiles";
    $TargetFile = "/etc/work/hostfiles/hosts";
    `cp $TargetFile /etc/work/hosts.workcopy`;
    `chmod 777 /etc/work/hosts.workcopy`;
    `mv $TargetFile $TargetFile.orig.$datefile`;
          
}
sub editPlace
{
    #$datefile = `date '+%m%d%y'`;
    local(*thisIP) = @_;
    $WorkCopy = "/etc/work/hosts.workcopy";
        open(HOSTS, $WorkCopy) || die "Can't open hosts.workcopy $!\n"
+;
        LINE: while(<HOSTS>)
    {       
        next LINE if /^#/;        
        next LINE if ! /$thisIP[0]/;        
           ($IP, $longhostname, $shorthostname, $devicealias)=split(" 
+");     
         print "$IP\t $longhostname\n";    
    
        
    }     
    close(HOSTS);
}

It's not done, but you can see the idea arising.
[download]