Hi, I really dont know perl, and I have and assignment of write this perl code in C++ can someone help me in the part of the math, I understand that words frequency need to be count and how to filter the words but the part of the math I really dont understand well. Please someone help me I need to finish this project.

use strict;
use DB_File;
 
# Hash with two levels of keys: $words{category}{word} gives count of
# 'word' in 'category'.  Tied to a DB_File to keep it persistent.
 
my %words;
tie %words, 'DB_File', 'words.db';
 
# Read a file and return a hash of the word counts in that file
 
sub parse_file
{
    my ( $file ) = @_;
    my %word_counts;
 
    # Grab all the words with between 3 and 44 letters
 
    open FILE, "<$file";
    while ( my $line = <FILE> ) {
        while ( $line =~ s/([[:alpha:]]{3,44})[ \t\n\r]// ) {
            $word_counts{lc($1)}++;
        }
    }
    close FILE;
    return %word_counts;
}
 
# Add words from a hash to the word counts for a category
sub add_words
{
    my ( $category, %words_in_file ) = @_;
 
    foreach my $word (keys %words_in_file) {
        $words{"$category-$word"} += $words_in_file{$word};
    }
}
 
# Get the classification of a file from word counts
sub classify
{
    my ( %words_in_file ) = @_;
 
    # Calculate the total number of words in each category and
    # the total number of words overall
 
    my %count;
    my $total = 0;
    foreach my $entry (keys %words) {
        $entry =~ /^(.+)-(.+)$/;
        $count{$1} += $words{$entry};
        $total += $words{$entry};
    }
 
    # Run through words and calculate the probability for each categor
+y
 
    my %score;
    foreach my $word (keys %words_in_file) {
        foreach my $category (keys %count) {
            if ( defined( $words{"$category-$word"} ) ) {
                $score{$category} += log( $words{"$category-$word"} /
                                          $count{$category} );
            } else {
                $score{$category} += log( 0.01 /
                                          $count{$category} );
            }
        }
    }
    # Add in the probability that the text is of a specific category
 
    foreach my $category (keys %count) {
        $score{$category} += log( $count{$category} / $total );
    }
    foreach my $category (sort { $score{$b} <=> $score{$a} } keys %cou
+nt) {
        print "$category $score{$category}\n";
    }
}
 
# Supported commands are 'add' to add words to a category and
# 'classify' to get the classification of a file
 
if ( ( $ARGV[0] eq 'add' ) && ( $#ARGV == 2 ) ) {
    add_words( $ARGV[1], parse_file( $ARGV[2] ) );
} elsif ( ( $ARGV[0] eq 'classify' ) && ( $#ARGV == 1 ) ) {
    classify( parse_file( $ARGV[1] ) );
} else {
    print <<EOUSAGE;
Usage: add <category> <file> - Adds words from <file> to category <cat
+egory>
       classify <file>       - Outputs classification of <file>
EOUSAGE
}
 
untie %words;
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