#!/usr/bin/perl -w

use strict;

if( $#ARGV != 1 )
{
   die "$0 <template> <source>\n";
}

my $file;
open $file, "<$ARGV[0]" or die $!;
my @template = <$file>;
close $file;

open $file, "<$ARGV[1]" or die $!;
my $source = join '', <$file>;
close $file;
$source =~ s/\s//gs;

my $i = 0;
foreach my $line (@template)
{
   foreach my $c (unpack 'C*', $line)
   {
      $c = chr($c);
      if( $c =~ /\s/s )
      {
         print $c;
      }
      else
      {
         die "Template too large\n" if $i > length($source);
         print substr($source, $i++, 1);
      }
   }
}

die "Template too small\n" if $i < length($source);