SPUG:Reference question

[Damian Conway]

Thane Williams wrote:

> Ok, maybe someone can point out the obvious to me here. Here's my code:
> 
> #!/usr/bin/perl
> my %record
> $record{Wilma}{age} = 32;
> $record{Fred}{age} = 38;
> $record{Wilma}{sex} = "female";
> $record{Fred}{sex} = "male";
> 
> foreach my $key (keys %record) {
>     my $age = $record{$key}{age};
>     my $sex = $record{$key}{sex};

Lexical scalars used.

> 
>     foreach ("age", "sex") {
>         print "$_ for $key is ${$_}\n";
>     }
> }
> 
> The foreach loop prints this:
> age for Fred is
> sex for Fred is
> age for Wilma is
> sex for Wilma is
> 
> If $_ equals "age", I'd expect ${$_} to equal $age.. which it apparently
> doesn't. (I get the same results even if I put "my $age = 50;").
> 
> I tried this test code:
> 
> #!/usr/bin/perl
> $name = "Fred";
> $age = "55";
> $sex = "male";

Package scalars used.

> foreach ("age", "sex") {
>     print "$_ for $name is ${$_}\n";
> }  
> And it works! What's the difference?

${$_} is ${"name"} or ${"age"}.
These are symbolic dereferences.
Symbolic dereferences always end up at a package variable, never a lexical.

HTH,

Damian