my $sentence_file = '/path/to/sentence.txt';

open($fh,"<",$sentence_file) or die "Could not open $sentence_file: $!";
while (my $sentence = <$fh>) {
	chomp $sentence;
	my @words = split(' ',$sentence);
	my %test;
	$test{$_}++ for @words;
	my $probability = $categorizer->predict(attributes => \%test);
	# ...
	# do what you need with $probability
}
close($fh);