#!/usr/bin/perl -w
use strict;

my %dictionary = ('dog' => 'pet', 'horse' =>'animal', 
                  'doggie' => 'also a pet',
                  'Bob' => 'person');

sortDictionary();

sub sortDictionary 
{
   foreach my $key (sort keys %dictionary) 
   {
     # process only keys with lower case first letter
     # e.g. 'Bob' => 'person' would be skipped
     
     my $first_letter;
     next unless (($first_letter) = $key =~ /^([a-z])/); 
      
     my $line = $key . '/' . $dictionary{$key};
     print "processing line: $line\n";
      
     writeFiles( $first_letter, $line);
   }
}

sub writeFiles 
{
   my ($first_letter, $line) = @_;
   
   my $filename = $first_letter . "_words.txt";
   print "file: $filename adding $line\n";
   
   open FILE, '>>', $filename or die "can not open $filename $!";
   print FILE "$line\n";
   close FILE;
      
   return;
}

__END__
processing line: dog/pet
file: d_words.txt adding dog/pet
processing line: doggie/also a pet
file: d_words.txt adding doggie/also a pet
processing line: horse/animal
file: h_words.txt adding horse/animal