> -----Original Message-----
> From: Michael Fowler [mailto:[EMAIL PROTECTED]]
> Sent: Thursday, October 04, 2001 9:37 PM
> To: Curtis Poe
> Cc: '[EMAIL PROTECTED]'
> Subject: Re: how to tell if hash value is null vs missing
>
>
> On Thu, Oct 04, 2001 at 04:34:17PM -0700, Curtis Poe wrote:
> > --- "Collins, Joe (EDSI\\BDR)" <[EMAIL PROTECTED]> wrote:
> > > $value=$myhash{$mykey};
> > > if $mykey is not a valid key, then $value still becomes ""
> >
> > If $mykey does not exist in the hash, then trying to access it will
> > "autovivify" that hash element (with no warnings, even if
> you have them
> > on) and the value will be undef, not the empty string.
>
> That's slightly incorrect, as well. The key will not be
> autovivified; if
> the key doesn't exist, accessing it won't make it exist.
>
> So, if the key $mykey doesn't exist then $value will be
> undef, and %myhash
> will remain unaltered.
True, but what can happen is something like this:
if ($myhash{$mykey}{a}) { ... }
This *will* create $myhash{$mykey} if it didn't exist before,
initializing it to a reference to an empty hash.
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