for my $key (keys %$results) {
...
}
[download]

Good luck!

Ira,

Chizz, it works! Thanks!!!
Seems I have to learn a lot more about hashes than I know by now... ;-)

Micha

my $hash = do 'hash.pl';
print $! || $@ || $hash->{'key'};
[download]

Thanks, I'll give it a try!
As I come from Pascal and Fortran77 (*yikes*) I still have some problems with the more advanced (say: efficient) way of accessing data in Perl.
And I will need ages to be able to reply properly and not a thousand times like above... ;)

Micha

In general, if you've got a reference to a hash - let's call it $ref - then you can work with it like this:

#construct a ref to an anonymous hash:
my $ref = {andy => 'likes cake'}; #note *curly* brackets
#another way
my %hash = (andy => 'likes beer too'); $ref = \%hash; #normal brackets
+ of course

#get at one specific value
print $ref->{andy};
#another way
print $$ref{andy};

#get all the keys
print keys %$ref;
#get all the values
print values %$ref;
#get key/value pairs
while (my ($key, $val) = each %$ref) {print "$key = $val"}

#copy the hash into a new hash
my %newhash = %$ref

#if you use the -> syntax with references to references, then you can 
+omit the ->s, after the first one, like this:
my $ref = { andy => {eats => 'cake'}};
print $ref->{andy}{eats}; #note only one -> necessary
[download]

hth,
andy.

update: and the book "Effective Perl Programming" has an excellent explanation, very full, with pictures.

Hi Andy,

I got a question concerning dereferencing hashes and use strict;.
I have a reference to a hash, derived from a reference to a nested hash:

my $hashref = $nested->{"key_to_hash"};

When I dereference that $hashref via

line 35:   my %realhash = %{$hashref};

and when I "use strict" I get the following message:

Can't use an undefined value as a HASH reference at
      /home/user/programming/perl/perlscript.pl line 35 (#1)
    (F) A value used as either a hard reference or a symbolic referenc
+e must
    be a defined value.  This helps to delurk some insidious errors.
[download]

Line 35 is the line where I dereference from $hashref.
When I don't use strict everything works fine...I got no idea what means "defined value" here. All my refs and vars are defined, or am I wrong?

Have a nice day and thanks for the tips yesterday!
Micha

Hi again Misha, here's my $.2,

Well, this line (which I think is equivalent) works ok:

perl -e 'my $nested = { key_to_hash => {data => "here"}}; print %{$nes
+ted->{key_to_has
h}};'
[download]

The error message simply means that $hashref is undefined, i.e. the scalar called 'hashref' contains no value. So this means that there is a problem with $nested->{key_to_hash} - maybe the key key_to_hash doesn't exist, or the value is undefined. Maybe $nested is pointing to the wrong hash.

An easy way to see what's gone wrong is to use the module Data::Dumper - which is standard, so you probably have it. Do this:

use Data::Dumper;
print Dumper($nested);
[download]

and you'll see the contents of the hash referred to by $nested.

If you can't see what's up with it, post the code where you set up $nested.

Have a nice day and thanks for the tips yesterday!
That's ok, you too.

andy.

You can use either

keys %{$hashref};
values %{$hashref};
[download]

or more short syntax

keys %$hashref;
values %$hashref;
[download]

You could also do :  my %real_hash = %$results which will attempt to copy your hash, but will not do a deep copy. If you need a better copy, you can use the Clone module to do that.

-----------------------------------------------------
Dr. Michael K. Neylon - mneylon-pm@masemware.com || "You've left the lens cap of your mind on again, Pinky" - The Brain
"I can see my house from here!"
It's not what you know, but knowing how to find it if you don't know that's important