Beefy Boxes and Bandwidth Generously Provided by pair Networks
The stupid question is the question not asked
 
PerlMonks  

Why does passing a subroutine an undefined element in a hash create it?

by faq_monk (Initiate)
on Oct 08, 1999 at 00:20 UTC ( #634=perlfaq nodetype: print w/replies, xml ) Need Help??

Current Perl documentation can be found at perldoc.perl.org.

Here is our local, out-dated (pre-5.6) version:

If you say something like:

    somefunc($hash{"nonesuch key here"});

Then that element ``autovivifies''; that is, it springs into existence whether you store something there or not. That's because functions get scalars passed in by reference. If somefunc() modifies $_[0], it has to be ready to write it back into the caller's version.

This has been fixed as of perl5.004.

Normally, merely accessing a key's value for a nonexistent key does not cause that key to be forever there. This is different than awk's behavior.

Log In?
Username:
Password:

What's my password?
Create A New User
Chatterbox?
[Corion]: Hmm - is anybody aware of a "protocol-only" HTTP module? I'd like to teach Prima non-blocking HTTP ideally without using threads, but that means reimplementing/ rewriting something like HTTP::Tiny (except asynchronous) or AnyEvent::HTTP
[Corion]: Ideally, the HTTP state machine but with a way to feed it HTTP data whenever I get it instead of it actively doing stuff.

How do I use this? | Other CB clients
Other Users?
Others wandering the Monastery: (9)
As of 2016-12-07 15:06 GMT
Sections?
Information?
Find Nodes?
Leftovers?
    Voting Booth?
    On a regular basis, I'm most likely to spy upon:













    Results (128 votes). Check out past polls.