my $otherhash; 
open FILE2, "< file2.txt"; 
while (my $line = <FILE2>) { 
   if ($line =~ /(k\d+)$/) { 
      $otherhash{$ke} = $myhash{$ke}; 
   } 
} 
close FILE2;

#!/usr/bin/perl 
 
use strict; 
use warnings; 
use Tie::File; 
 
open my $template, '<', 'key_value' or die "Can't open 'key_value' $!"; 
tie my @auto_it, 'Tie::File', 'auto_it' or die "Can't open 'auto_it' $!"; 
 
my %template; 
while ( <$template> ) { 
    chomp; 
    my ($key, $value) = split /=/; 
    $template{$key} = $value; 
} 
 
(tied @auto_it)->defer; 
for ( @auto_it ) { 
    $_ = "$1$template{$2}" if /^(.+)(k\d+)$/ and exists $template{$2}; 
} 
untie @auto_it;