use strict;

my $filename = "words";

#   hash: starts with %.
my %digitWords;

my %letterValues =
   ('a' => '2',
    'b' => '2',
    'c' => '2',
    'd' => '3',
    'e' => '3',
    'f' => '3',
    'g' => '4',
    'h' => '4',
    'i' => '4',
    'j' => '5',
    'k' => '5',
    'l' => '5',
    'm' => '6',
    'n' => '6',
    'o' => '6',
    'p' => '7',
    'q' => '7',
    'r' => '7',
    's' => '7',
    't' => '8',
    'u' => '8',
    'v' => '8',
    'w' => '9',
    'x' => '9',
    'y' => '9',
    'z' => '9');

#   IN: filehandler
open IN, $filename;

while ($_ =  <IN>) {
   chomp;
   my $word = lc($_);

   #    Skip if there is non-alphabets
   next if /[^a-z]/;

   #    Get the corresponding digit string.
   my $digits = "";
   foreach $_ (split //, $word) {
       $digits .= $letterValues{$_};
   }

   $digitWords{$digits} = $digitWords{$digits} ? ( $digitWords{$digits} . ", " . $word)
                                               : $word;
}
close IN;

while (1) {
   print "Please input a number or 'q' to quit: ";
   my $input = <>;
   chomp($input);
   last if $input =~ /^q$/i;
   if ($digitWords{$input}) {
       print "Words of $input is $digitWords{$input}.\n\n";
   }
   else {
       print "Sorry, there is no Word for $input.\n\n";
   }
}

exit 0;