Re: Concise idiom sought

• Subject: Re: Concise idiom sought

 <Tim Kazner> wrote in comp.lang.perl.misc:
> On 29 Mar 2006 07:29:50 GMT, anno4000@xxxxxxxxxxxxxxxxxxxxxxx (Anno
> Siegel) wrote:
> > <Tim Kazner> wrote in comp.lang.perl.misc:
> >> On Mon, 27 Mar 2006 09:05:37 +0200, "Dr.Ruud"
> <rvtol+news@xxxxxxxxxxxx> wrote:
> >> >Randal L. Schwartz schreef:
> >> >
> >> >>         defined $_ or $_ = 1 for $base_ref->{pl};

[...]

> use strict;
> use warnings;
> 
> my ($base_ref,$v) = ({});
> 
> $$v=1 if ($v=\$base_ref->{pl} and !defined $$v);
> print "$$v\n";
>  
> ($base_ref,$v) = ({pl=>8});
> 
> $$v=1 if ($v=\$base_ref->{pl} and !defined $$v);
> print "$$v\n";
> 
> __END__
> 1
> 8

What is the advantage over

   defined or $_ = 1 for $base_ref->{pl};

Especially considering that $v is undeclared.  That would also have
to be done somewhere.

> Not really sure why this won't work:
> 
> $$v=1 if (!defined $($v=\$base_ref->{pl}));

That fails because de-referencing doesn't take an arbitrary expression.
You must give it a simple variable or a block:

    $$v=1 unless defined ${ $v=\$base_ref->{pl} };

Again, what is the possible advantage?

Anno
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