I don't think that the string functions are the way to go here. I would use regex to make 2 hashes and then merge/adjust them in whatever way that you need. This is some example code: 
#!/usr/bin/perl -w
use strict;
use Data::Dumper;

open (my $config_file_main   ,"<","config18.txt" )or die $!;
open (my $config_file_update ,"<","config27.txt" )or die $!;

my %file1 = read_cfg ($config_file_main);
my %file2 = read_cfg ($config_file_update);

# this combines both hashes into one !!!!
# A simple "merge" operation.
# More complex things can be done

%file1 = (%file1, %file2);

# Usually it is better to print in
# a human readable format with sort
#
foreach my $key (sort keys %file1)
{
   print "$key = $file1{$key}\n";
}

# This returns a list instead of list ref
# Of course using a ref is more efficient, but here I
# do something simple to illustrate points above..
#
sub read_cfg
{
   my $file_handle = shift;
   my %hash;
   
   while (<$file_handle>)
   {
      next if /^\s*$/;          #skip blank lines
      my ($name,$value) = $_ =~ /^\s*(\S+)\s*=>\s*(\S+)/;
      $hash{$name} = $value;
   }
   close ($file_handle);
   return %hash;   
}

[download]
config27:
CONFIG_BRIDGE_NF_EBTABLES => m
CONFIG_BRIDGE_EBT_BROUTE => y
CONFIG_BRIDGE_EBT_T_FILTER => z

[download]
config18:
CONFIG_BRIDGE_NF_EBTABLES => m
CONFIG_BRIDGE_EBT_BROUTE => m
CONFIG_BRIDGE_EBT_T_FILTER => m
CONFIG_BRIDGE_EBT_T_NAT => m
CONFIG_BRIDGE_EBT_802_3 => m
CONFIG_BRIDGE_EBT_AMONG => m
CONFIG_BRIDGE_EBT_ARP => m
CONFIG_BRIDGE_EBT_IP => m
CONFIG_BRIDGE_EBT_LIMIT => m
CONFIG_BRIDGE_EBT_MARK => m
CONFIG_BRIDGE_EBT_PKTTYPE => m
CONFIG_BRIDGE_EBT_STP => m
CONFIG_BRIDGE_EBT_VLAN => m
CONFIG_BRIDGE_EBT_ARPREPLY => m
CONFIG_BRIDGE_EBT_DNAT => m
CONFIG_BRIDGE_EBT_MARK_T => m
CONFIG_BRIDGE_EBT_REDIRECT => m
CONFIG_BRIDGE_EBT_SNAT => m
CONFIG_BRIDGE_EBT_LOG => m
CONFIG_BRIDGE_EBT_ULOG => m

[download]
Prints: 
CONFIG_BRIDGE_EBT_802_3 = m
CONFIG_BRIDGE_EBT_AMONG = m
CONFIG_BRIDGE_EBT_ARP = m
CONFIG_BRIDGE_EBT_ARPREPLY = m
CONFIG_BRIDGE_EBT_BROUTE = y
CONFIG_BRIDGE_EBT_DNAT = m
CONFIG_BRIDGE_EBT_IP = m
CONFIG_BRIDGE_EBT_LIMIT = m
CONFIG_BRIDGE_EBT_LOG = m
CONFIG_BRIDGE_EBT_MARK = m
CONFIG_BRIDGE_EBT_MARK_T = m
CONFIG_BRIDGE_EBT_PKTTYPE = m
CONFIG_BRIDGE_EBT_REDIRECT = m
CONFIG_BRIDGE_EBT_SNAT = m
CONFIG_BRIDGE_EBT_STP = m
CONFIG_BRIDGE_EBT_T_FILTER = z
CONFIG_BRIDGE_EBT_T_NAT = m
CONFIG_BRIDGE_EBT_ULOG = m
CONFIG_BRIDGE_EBT_VLAN = m
CONFIG_BRIDGE_NF_EBTABLES = m

[download]

In reply to Re: Hash , Keys strangely chopped !! by Marshall
in thread Hash , Keys strangely chopped !! by onkar

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.