sub elabora_st {
 # argument list:
 # action='prepare' or action='finish'
 # then the hash delle query
 
  my $action=shift @_;

   my %q=@_;

   

  for my  $value (values %q ){


   
    for my $sel ( @$value ) { 
    
       # print  "$sel->[0]\n";
    
	if ( $action  eq 'prepare') {
	 
	     #  print "$sel->[0] \n";
	       my $sth=$dbh->prepare($sel->[0]);
     	   $sel->[1]=$sth;
	}
  	
	elsif ($action eq 'finish') {
		# to do
	}
   
     }
   }

}