Well, this isn't really a DBI question.

First you can use the hash reference inside of the scalar very similar to a normal hash, just use $$hash{foo}:

  my $hash_ref = {
  a => 1 ,
  b => 2 ,  
  } ;
  
  print "$$hash_ref{a}\n" ;
  print "$$hash_ref{b}\n" ;
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But if you really want to use $hash{foo} directly, without make a copy, use this code:

  my $hash_ref = {
  a => 1 ,
  b => 2 ,  
  } ;
  
  local(*hash) ;
  *hash = $hash_ref ;

  print "$hash{a}\n" ;
  print "$hash{b}\n" ;
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But note that %hash is declared inside *hash, with local() to simulate the my %hash! And any other variable or handle with the name hash will be overwrited. In other words, local() works for: $hash, @hash, %hash, hash

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