Don't understand output

this code is supposed to take in two files one which has a language in the form of:
in 0.021268266230653
er 0.0199459816856101
an 0.0180031452539636
he 0.0167558696165399
on 0.0161781277728501
th 0.0155111263808014
re 0.0127007970702476

and another which takes in song titles like:
this is a song title1 (4.30)
this is a song title2 (4.30)

I want to split the information from the second file (per word) into bigrams and then get the corresponding frequencies from my language model then calculte the probability of that word being in the model. so (4.30) should return a probability of 0 but it doesn't. Anyone know why?

How is the code? Is there any way I could tidy it up a bit?

thanks.

Code:
#!usr/bin/perl
use strict;
use warnings;
use diagnostics;
use POSIX qw(log10);
use FileHandle;

#open file handles for languagemodel and test file
my $fh = new FileHandle;
my $fh2 = new FileHandle;
$fh->open("<$ARGV[0]") or die "could not open file\n";
$fh2->open("<$ARGV[1]") or die "could not open file\n";

#open a file to output the results to
open(OUTTRACKS,">trackbigrams") or die "could not open trackbigrams\n";

my $line;
my %bigramfrequency;
my $totalbigram;
my %bititles;
my @titlesbigram;
my @bifrequency;
my @frequency;
my @letterline;
my $result;
my $word;

#subroutine to get bigrams
sub bigram()
{
       
         
         for (my $i=0; $i <= $#letterline-1; $i++)
         {
          my $bigram = $letterline[$i] . $letterline[$i+1];
          $bigramfrequency{$bigram}++;
          $totalbigram++;
         }
    $_ /= $totalbigram foreach values %bigramfrequency;
    return %bigramfrequency;
}



#read in the language model values into a hash table
sub buildlanguage($)
{
   my $filehandle = shift;
   my %languagemodel;

   while (<$filehandle>)
   {
      chomp;
      my ($key, $value) = split /\s/, $_, 2;
      $languagemodel{$key} = $value;
   }
   return %languagemodel;
}

#build the language model from the first file passed in
my %model = buildlanguage($fh);

#subroutine to get the corresponding frequency for the bigrams
sub lookupfreq
{
for (my $i=0; $i<@titlesbigram; $i++) {
   if (exists $model{$titlesbigram[$i]})
      {
       $frequency[$i] = $model{$titlesbigram[$i]};
       }
     else
     {
     $frequency[$i] = 0;
     }
      }
return @frequency;
}

#calculate the probability
sub getProbability
{
my $run_total;
 foreach (@bifrequency)
 {
  $run_total += $_;
  }

my $nth_root = scalar(@bifrequency);
my $log_e = log10($run_total);
my $prob = exp($log_e/$nth_root);
return $prob;
}

#open a file handle for the test file
my $fileHandle2 = $fh2;


while (<$fileHandle2>)
     {
     $line = $_;
     chomp $line;
     $line = lc($line);

     #wordline contains each word of the string
     my @wordline =  split /[^\p{IsL}\d()]+/, $line;
     
     foreach $word (@wordline)
               {
     #letter line contains just a letter
        @letterline = split //, $word;
     %bititles = bigram();
     @titlesbigram = keys (%bititles);
     @bifrequency = lookupfreq();
     $result = getProbability();
     print OUTTRACKS "$word\t $result\n"
          }
     }
$fh->close();
$fh2->close();
close(OUTTRACKS);