I tried to run my programme using WordNet::Similarity module which works in ommandlines for me but i get the undef values in my output matrix while my input is a simple 4 words corpus(each word per line). any special reason?

 #! /usr/local/bin/perl -w 

use strict;
use warnings;
use WordNet::QueryData;
use WordNet::Similarity::random;
use WordNet::Similarity::path;
use WordNet::Similarity::wup;
use WordNet::Similarity::lch;
use WordNet::Similarity::jcn;
use WordNet::Similarity::res;
use WordNet::Similarity::lin;
use WordNet::Similarity::hso;
use WordNet::Similarity::lesk;
use WordNet::Similarity::vector; 
use WordNet::Similarity::vector_pairs; 
use Data::Dumper;

my $Infile = shift;
my $Outfile = shift;
my $Measure = shift;
my (@sim , $simi);

unless (defined $Infile and defined $Outfile and defined $Measure) {
    print STDERR "Undefined input\n";
    print STDERR "Usage: simmat.pl inputfile outputfile measure()\n";
        exit 1;
}
 print STDERR "Loading WordNet... ";
my $wn = WordNet::QueryData->new;
die "Unable to create WordNet object.\n" if(!$wn);
print STDERR "done.\n";


open (INPUT, "$Infile") || die "can't open the input file";
my @words = <INPUT>;
close (INPUT) ;

for my $i (0 .. $#words) {
    for my $j ( ($i+1) .. $#words) {
        $sim[$i][$j] = similarity( $words[$i], $words[$j]);
        $sim[$j][$i] = $sim[$i][$j];
           }
}

sub similarity {
   my ( $w1, $w2 ) = @_;
   $simi = 1;
   my $obj = $Measure -> new($wn);
   my $simi = $obj-> getRelatedness("$w1#n#1", "$w2#n#1");
   return $simi;
}

open (OUTPUT, ">$Outfile");
print OUTPUT Dumper(\@sim);
close(OUTPUT);
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output :

$VAR1 = [
          [
            undef,
            undef,
            undef,
            undef
          ],
          [
            undef,
            undef,
            undef,
            undef
          ],
          [
            undef,
            undef,
            undef,
            undef
          ],
          [
            undef,
            undef,
            undef
          ]
        ];
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