There is more discussion about this here: https://www.perlmonks.org/?node_id=11151225 as this also caught me out.

Most languages don't have autovivication which I think is why it catches so many people. My general thoughts on this is autovivication is overall more useful.

Example: If you have a JSON structure in an object and you want to check if a certain item in the structure exists with a value, in javascript to avoid throwing an error it is extremely annoying:

if (json && json.command && json.command.results && json.command.results[0] && json.command.results[0].code && (json.command.results[0].code == 9))

But in perl with autovivificatin, its much nicer:

if ($json->{command}{results}[0]{code}//0 == 9)

In reply to Re: Defined test creates non-empty hash value by sectokia
in thread Defined test creates non-empty hash value by glendeni

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.