I would like to add a second vote for use Memoize; your lookup functions are expensive and read-only, exactly what memoization is good for.

In addition to the behavior ariels mentions above, I'd like to point out it is easy to persistantly store the memoized data using tie, no muss, no fuss. 

        use DB_File; 
        tie my %cache => 'DB_File', $filename, O_RDWR|O_CREAT, 0666;
        memoize 'function', SCALAR_CACHE => [HASH => \%cache];

[download]
In addition, Memoize makes a good profiler-- details are available here in Dominus's article. 

___
-DA
> perl -MPOSIX -e'$ENV{TZ}="US/Eastern";print ctime(10**9)'
Sat Sep  8 21:46:40 2001

[download]

In reply to Re: Re: Using tie to initialize large datastructures by da
in thread Using tie to initialize large datastructures by htoug

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.