Growing a Hash of Hashes via its reference

Henri has asked for the wisdom of the Perl Monks concerning the following question:

Dear Monks,

I would like to modify (grow) a hash of hashes iteratively within a loop through a subroutine and in the end print what's stored in the hash. To do this I am passing a reference to the hash to the subroutine - at least I thought so. However, I get the error "Global symbol "%misfits" requires explicit package name at ...". This is the code that I can't get to work:

#Main
my @whole_world = ();
my $misfits = {};   # the reference

foreach my $individual (@whole_world) {
    ($ok_ones, $misfits) = find_misfits(\@whole_world, $misfits);
}

print_misfits($misfits);

# sub
sub find_misfits {
    my ($whole_world, $misfits) = @_;

    my %candidates = ();

    # do stuff to find the misfits, ie compare the genetic setup of in
+dividuals

    # add individuals that don't fit to $misfits
        $misfits{$stand}{$mother}{$offspring} = {%{$candidate{$stand}{
+$mother}{$offspring}}};

    return ($misfits, some more structures);
}
[download]

Any help would be greatly appreciated.

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Re: Growing a Hash of Hashes via its reference by almut (Canon) on Feb 17, 2009 at 19:41 UTC
`$misfits{$stand}{$mother}{$offspring}` You probably want: `$misfits->{$stand}{$mother}{$offspring}` [download] Without the arrow, Perl thinks you want to access a hash `%misfits`, not a hash reference (how should it disambiguate?), and thus `use strict` is complaining...	[reply] [d/l] [select]
Re: Growing a Hash of Hashes via its reference by Bloodnok (Vicar) on Feb 17, 2009 at 19:41 UTC
In sub `find_misfits`, `$misfits` is a hash ref., so you need to change... `$misfits{$stand}{$mother}{$offspring} = {%{$candidate{$stand}{$mother} +{$offspring}}};` [download] to read `$misfits->{$stand}{$mother}{$offspring} = {%{$candidate{$stand}{$mothe +r}{$offspring}}};` [download] A user level that continues to overstate my experience :-))	[reply] [d/l] [select]
Re: Growing a Hash of Hashes via its reference by toolic (Bishop) on Feb 17, 2009 at 19:35 UTC
Maybe you need to localize `$misfits` in `sub find_misfits`? `my ($whole_world, $misfits) = @_;` [download] It is difficult to say because the code you posted has syntax errors and is not a complete example that we can run. So, we can not duplicate your error. The strictures will probably help you: `use warnings; use strict; use diagnostics;` [download]	[reply] [d/l] [select]
Re: Growing a Hash of Hashes via its reference by Henri (Novice) on Feb 17, 2009 at 20:02 UTC
Thanks for the solution. Henri	[reply]