As an example of what BrowserUk and GrandFather are talking about, print the addresses of the hash references you're passing around: 

c:\@Work\Perl\monks>perl -wMstrict -MData::Dumper -le
"my $hash = {};
 print 'Ma: ', $hash;
 ;;
 do_something($hash);
 ;;
 print 'Mb: ', $hash;
 print Dumper($hash);
 ;;
 sub do_something {
   my $hash = shift;
   print 'Sa: ', $hash;
   ;;
   $hash = { a => 'alpha',  b => 'beta', };
   print 'Sb: ', $hash;
   print Dumper( $hash );
   }
"
Ma: HASH(0x9cd06c)
Sa: HASH(0x9cd06c)
Sb: HASH(0x9cd16c)
$VAR1 = {
          'a' => 'alpha',
          'b' => 'beta'
        };

Mb: HASH(0x9cd06c)
$VAR1 = {};

[download]
Note that the address of the  $hash reference variable in the subroutine changes between point Sa and point Sb when you assign another anonymous hash reference to it, but the  $hash reference variable in the "main" part of the code never changes its address (or its contents).

Replace the
    $hash = { a => 'alpha',  b => 'beta', };
statement in the subroutine with
    $hash->{a} = 'alpha';
    $hash->{b} = 'beta';
statements that assign by reference to the referent and see what happens to all the hash reference addresses: they never change.

Give a man a fish:  <%-{-{-{-<

In reply to Re: hash question by AnomalousMonk
in thread hash question by duyet

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