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

Hi, I need help with a program I'm trying to right where I need to get specific values from a hash table and return them. I'll try my best to explain where I have to pull these elements from. The hash table has the structure: 
%hash -> $variable_name -> 'fixed name(s)' -> value

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I'm trying to assign the "value" to a scalar and return it but so far I'm not having any luck. $variable_name is being generated by a foreach loop and is definitely working. I've been trying code along the lines of 
my $value = values %{$hash{$variable_name}{'fixed name'}};
print $value;

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But this gives me "0". Which it's not. print Dumper %hash shows a nice hash table containing all the data it should so I know it's there. Can someone tell me what I'm doing wrong here?

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Re: How to get specific hash elements?
by kyle (Abbot) on May 14, 2007 at 15:35 UTC

    First, values returns a list of values, not just a single value. You're assigning it in scalar context, so what you're getting is the number of values that it would return if you'd used it in a list context. That said, I suspect that values isn't even what you want to be using.

    If you do an assignment like this (I can't see the foreach loop you say is working): 

    $hash{$variable_name}{'fixed name'} = 'val-you';

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    ...then you can get that value out with the same expression you used in the assignment ($hash{$variable_name}{'fixed name'}).

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Re: How to get specific hash elements?
by MonkE (Hermit) on May 14, 2007 at 15:39 UTC

    If I understand you correctly, you should be able to use $hash{$variable_name}{'fixed name'} both as an lvalue or an rvalue.

    Try this (tested):

    use strict;
my %hash;
$hash{'test1'}{'fixed name'} = 42;
my $variable_name = 'test1';
print $hash{$variable_name}{'fixed name'};
print "\n";

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    When executed, it prints 42.

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      Tried this format and it's giving me "Use of uninitialized value in print at ./testScript.pl line 10". My hash is actually of the form: 
      $VAR1 = 'Variable_name1                         ';
$VAR2 = {
          'Fixed_name1     ' => {
                            'value    ' => undef
                          },
          'Fixed_name2   ' => {
                            'value    ' => undef
                          }
        };
$VAR3 = 'Variable_Name2                                    ';
$VAR4 = {
          'Fixed_name1       ' => {
                            'value    ' => undef
                          },
          'Fixed_name2   ' => {
                            'value    ' => undef
                          }
        };

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      I don't know why it's pointing the values to undefined at the end. "value" is the thing I'm looking for. Thanks for the help guys. Been stuck on this for a few days and it's beginning to annoy me
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        What's with all the white space at the end of your keys? That's going to cause problems: 'Fixed_name1     ' does not equal 'Fixed_name1'.

        -derby
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        Ah. Well, clearly, all the values of the "leaf" nodes in the structure are undef. What you want is the keys of the bottom level of the struct. E.g.: 

        my @values = keys %{ $hash{'test1'}{'fixed name'} };

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        A word spoken in Mind will reach its own level, in the objective world, by its own weight
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Re: How to get specific hash elements?
by jdporter (Paladin) on May 14, 2007 at 15:33 UTC

    Still not clear. Try posting an illustrative bit of the dump, and maybe some code that populates the structure. TIA.

    A word spoken in Mind will reach its own level, in the objective world, by its own weight
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Re: How to get specific hash elements?
by derby (Abbot) on May 14, 2007 at 15:33 UTC

    Is 'fixes name' one hash key or two? values returns all the values of a hash.

    -derby
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