self modifying perl code

noconfig.pl

#!/usr/env perl
use strict;use warnings;
my %config;
loadConfig();                               ##load config from __DATA__
foreach (sort keys %config){                
	print $_, "  =>  ",$config{$_},"\n__\n";# display config 
	print "Enter new Value for $_\n>>";     # offer to modify it
	chomp( $config{$_}=<>);                 # modify it
}
saveConfig();                               #save new config


sub loadConfig{                             # read keys and values from data
    my ($key, $value);
    while (my $line = <DATA>){
	   if ($line=~/\[([^\]]+)\]/){
		  $key=$1;
	   }
	   elsif($key  and $line!~/^\s*$/){
		   $config{$key}.=$line;
	   }
	};
	foreach (keys %config){
		$config{$_}=~s/\s*$//g;
		
	}
}
sub saveConfig{                  # save  config into data segment
    open my $readFile, '<', $0       or die "can't open $0:     $!";
    open my $tempFile, '>', $0.".tmp" or die "can't open $0.tmp: $!";
    while (<$readFile>){         # read own code
	   last if $_=~/^__DATA__/;    # store everithing upto the data
	   print $tempFile $_          # segment into a temporary file
	};
	close $readFile;       
	     
print $tempFile "__DATA__\n";    # now create a new __DATA__ segment
foreach (sort keys %config){     # store everything from config
  print $tempFile "[$_]\n$config{$_}\n\n";
}
close $tempFile;

unlink "$0.bak";                  # delete previous backups
rename $0, "$0.bak";              # backup current file
rename "$0.tmp", $0;              # make temp the new code
}

__DATA__
[bestFriend]
gertie

[birthDate]
12-12-12

[description]
not much is known, but likes blue, has gertie for a best friend and is 7

[favouriteColour]
blue