Technically if you want to see if the hashref $hash has an element for key $var you want exists. Even so neither of those two examples should force a copy of %{$hash} (at least I don't believe so; however if there were multiple levels there such that you trigger autovivification (i.e. $hash->{'not there'}->{$var}) it would probably force a copy since you're implicitly changing $hash's contents). And if you really want read-only then Readonly will make it enforced not just by convention.

You might also want to consider using something like BerkelyDB or DBD::SQLite to access your data from disk rather than pulling it all into RAM.

Update: Or Cache::Memcache might be worth looking into as well.

Update: Duur, Readonly not ReadOnly. Thanks to superfrink for the catch.

The cake is a lie.
The cake is a lie.
The cake is a lie.

In reply to Re: fork(): where does copy happen? by Fletch
in thread fork(): where does copy happen? by Anonymous Monk

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.