#!/usr/bin/perl
# merge.pl - Don Yang (uguu.org)
#
# 11/03/12

use strict;

die "$0 <primary> <secondary>\n" unless $#ARGV == 1;
my $file;
open $file, "< $ARGV[0]" or die $!;
my $primary = join '', <$file>;
close $file;
open $file, "< $ARGV[1]" or die $!;
my $secondary = join '', <$file>;
close $file;

die unless length($primary) == length($secondary);

for(my $i = 0; $i < length($primary); $i++)
{
   my $x = substr($primary, $i, 1);
   if( $x =~ /\s/ )
   {
      print substr($secondary, $i, 1);
   }
   else
   {
      print $x;
   }
}