How to test a tied HASH as a boolean?

Take a look in this code, and you can see that the HASH is always FALSE as boolean. 

  my %hash ;
  
  tie(%hash , 'TiedHash') ;
  
  print "key: $hash{key}\n" ;
  
  if ( %hash ) { print "BOOL: 1\n" ;}
  else { print "BOOL: 0\n" ;}

package TiedHash ;

  use overload (
  'bool' => sub{ print "OVER1!\n" ; } , ## print() return 1!
  '""' =>   sub{ print "OVER2!\n" ; } ,
  '0+' =>   sub{ print "OVER3!\n" ; } ,  
  'fallback' => 1 ,
  );

sub TIEHASH { bless({}, __PACKAGE__ ) ;}

sub FETCH { return( 'fetch_val' ) ;}

[download]
This was test on Perl-5.6.1-Win32 and Perl-5.8.0-Win32, with and without use overload and it always return FALSE!

Looking for a way to return TRUE for a tied HASH, I found that it looks for the value of the HASH not tied. Soo, the code that work is: 

  my %hash = (1) ;
  
  tie(%hash , 'TiedHash') ;
  
  if ( %hash ) { print "BOOL: 1\n" ;}
  else { print "BOOL: 0\n" ;}

package TiedHash ;

sub TIEHASH { bless({}, __PACKAGE__ ) ;}

[download]
In other words, the HASH need to have at least one KEY before TIE it, or the HASH will be FALSE as boolean!

I don't know if this is documented, but haven't found anything about it. I also think that it looks like a bug, since the value of the HASH as boolean (and string) need to be controled and changed (now is like a constant after tie it). The right way is to control this through overload or from some sub inside the TiedHash package (like FETCH).

Well, for me I just need to always have the HASH as TRUE, since I tie it only when I have keys. But in the future this can be changed in Perl, and my code wont work! I holp that I have helped some monks that had this problem too. ;-P

Graciliano M. P.
"The creativity is the expression of the liberty".

In reply to Tied HASH as boolean?! by gmpassos

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