I'm making the assumption that your definition of "phrase" requires that the words be contiguous in the original text. That would explain the missing "Camel Book" phrase. What I came up with is no shorter, but it works.

#!/usr/bin/perl
use strict;
use warnings;

my @words = qw(Camel Perl Book);

for my $phrase_length (1..@words) {
  for my $start_idx (0..(@words-$phrase_length)) {
    print "@words[$start_idx .. ($start_idx + ($phrase_length - 1))]\n
+";
  }
}
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