why would I want to do

You wouldn't. :-) I _think_ the issue the OP was refering to (but actually doesnt deal with) is the possibility that children is undef. Since the dereference is a fetch it wont be automagically created and the if ( @{...} ) will choke. Personally I would replace it and the for with the following 

for my $child ( @{ $t->{children} || [] } ) {
}

[download]

Normally I dont put so much whitespace in my expressions, but I figured here it makes things clearer, When dereferencing, if $t->{children} is false then we use an empty anonymous array to iterate over. We dont have to check if there are elements, because if there are, we _will_ iterate over them, and if there are, well, we _wont_.

BTW, Its a good idea to become quite familiar with binary trees before you play with n-ary trees. It helps to solidy the concepts. A good learning exercise is to implement a Tie::Hash using a binary tree. (Say a sorted hash implemented using a binary tree?) Incidentally any tree structure can be represented using binary trees if necessary so it pays off to understand them well.

HTH


---
demerphq

<Elian> And I do take a kind of perverse pleasure in having an OO assembly language...

In reply to Re: Re: Re: Recursion, tree parsing. by demerphq
in thread Recursion, tree parsing. by BUU

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.