This was bugging me for AGES ! So I thought I would register and give something back to the Monks.... This snippet does four things:

Passes a Hash by reference (function b)

Adds some key/value pairs to the hash

Prints the hash using a recursive function (so the hash can be in any form, i think)

Passes (in effect) the hashes within the main hash to the recursive function.

It's taken me a while to work out references in perl. I hope it is useful to someone. 

#!/opt/bin/perl5

my %c;

b(\%c);

#print as normal
if(0)
{
    for $i (keys %c)
    {
        print "$i = $c{$i}\n";
        for $a (keys %{$c{$i}})
        {
            print "$i = $c{$i} = $c{$i}{$a}\n";
        }
    }
}

sub b
{
    my($c)=@_;
    
    $$c{b} = 'b';
    $$c{c} = 'c';
    
    $$c{b}{a} = 'ba';
    $$c{b}{v} = 'bv';
    $$c{b}{v}{g} = 'bvg';
    
    print "printing c{b}{v} = $$c{b}{v}\n";
    
    recref($c,"");
}

#pass this function a reference to a hash
sub recref
{
    my($cref,$str)=@_;
    my $i;
    my $prefix;
    
    for $i (keys %{$cref})
    {    
        $prefix = $str . "." . $i;
        print "$prefix = $$cref{$i}\n";
        recref($cref->{$i},$prefix);
    }
}

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In reply to Passing Hashes by Reference by jamesdmorris

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