my %word_list = ( bat=> 0, cat=> 0, eat=> 0, fat=> 0 );
my @words = qw( bat bat dat fat eat eat eat fat );
my $word;

foreach $word (@words){
   if(exists $word_list{$word}){
      $word_list{$word}= $word_list{$word} + 1; 
   }
   else{
      $word_list{$word} = 1;
   }
}

foreach $word (sort keys %word_list) {
   print "$word: $word_list{$word}\n";
}