Returning a hash?

ken2 has asked for the wisdom of the Perl Monks concerning the following question:

I am confused on how to return a hash from a subroutine or if I can even return a hash... My subroutine defines a hash, populates it, and then returns it:

  sub savePurpose
  ...    
  my %hTptPurpose; 
  ...
  return \%hTptPurpose;
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The calling code is: my $hTableData = savePurpose($szXls);

One of the next things the Perl script tries after calling savePurpose is reference (what I'd like to be) the hash as: my @aTable = keys %hTableData;

I'm doing something very wrong as the error I get is: Global symbol "%hTableData" requires explicit package name at...
Can someone help me understand what I am doing wrong with this, keeping in mind that ideally I want to have a hash returned from savePurpose?

Thanks,
Ken

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Re: Returning a hash? by GrandFather (Saint) on Aug 24, 2006 at 02:34 UTC
Very nearly there. Remember you have a hash ref, not a hash, so you need to dereference it: `my @aTable = keys %$hTableData;` [download] Welcome to the mad house BTW. Nice first post. Update you may find perldsc helpful too. DWIM is Perl's answer to Gödel	[reply] [d/l]
Re^2: Returning a hash? by jdtoronto (Prior) on Aug 24, 2006 at 05:47 UTC
Naturally GrandFather is quite correct, BUT, I looked at his response and it took a moment to see that he was de-referencing the hash reference that is being returned. For precisely this reason, it is suggested in the book "Perl Best Practices" by thedamian (see p228-229) that when you need to use "prefix dereferencing" such as this, that you used braces around the reference: `%{$hTableData}` [download] is more noticeable, and thus readable than: `%$hTableData` [download] It makes the dereferencing easier to see in this case, and getting into this habit can make your dereferencing far easier to understand as you meet more complexes cases. I must also agree that perldsc is a most useful piece of reading. Welcome to the monastery! jdtoronto	[reply] [d/l] [select]
Re^2: Returning a hash? by ken2 (Novice) on Aug 24, 2006 at 02:45 UTC
Thank you! I'm off and running with the next challenge. Glad to have found this site.	[reply]