Need help on K nearest neighbourhood algorithm with perl

Can anyone explain each line of the code below and what does it do.
And from the code below i'm hoping to modify it so that it can determine which email is spam or which is not. If i m not mistaken it uses the K nearest neighbourhood algorithm to determine the difference. thx,

p.s. I have attached a sample of spam and non spam email text file to show their difference.
use Search::VectorSpace;
 
# These are just some simple sample documents
my @docs = (
	"The cat in the hat",
	"A cat is a fine pet.",
	"Dogs and cats make good pets.");
 
# Build our search engine, with a suitable threshold	
my $engine = Search::VectorSpace->new( docs => \@docs, threshold=>'0.1');
 
# Index the documents
$engine->build_index();
 
# Answer queries
print "Next query?\n";
while ( my $query = <> ) {
    my %results = $engine->search( $query );
    foreach my $result ( sort { $results{$b} <=> $results{$a} } keys %results ) {
        print "Relevance: ", $results{$result}, "\n";
        print $result, "\n\n";
    }
    print "Next query?\n";
}

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spam.txt
ychetAsked:
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