I noticed it too, that you score caps only. That said, if you score by length, it works nicely as well.
Another smart thing is to remove impossible words at earliest opportunity. 
  DOG: for my $dog (@_) {
    my $remaining = $letters;
    $remaining =~ s/$_//i or next DOG for split //, $dog;
    push @remain, $remaining;
    push @dogs, $dog;
  }
  while( my $dog = shift @dogs ) {
    dogtree( "$tree $dog", shift @remain, @dogs );
  }

[download]
The given puzzle solves in 1-2 secs, and takes about 3 minutes for a full pass (return instead of exit).
Only one solution exists. A letter set such as
"A(11),B(3),C(2),D(8),E(6),F(1),H(8),I(10),J(1),K(1),L(6),M(1),N(10),O(9),P(2),R(7),S(6),T(9),U(7),V(1),W(1),X(1),Z(2)"; takes some 20 times longer...

In reply to Re^4: Another word puzzle with too many permutations by oiskuu
in thread Another word puzzle with too many permutations by sarchasm

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.