when your get_info method is invoked with the infix notion, your $db_info object will implicitly be passed as the first argument... no need for your %db_info hash. you'll commonly see

sub get_info {
  my $self = shift;
  my $ID = shift; # or @_
  #whatever..
}
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which gives you a $self handle to your db_info instance (the this reference in some other languages). why don't you check out this section in perlobj.

cheers