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my @data = (); 
while (@data = $sth->fetchrow_array){
 print TSCH join(' ',@data),"\n";
}

while (my @data = $sth->fetchrow_array){
 print TSCH join(' ',@data),"\n";
}

Use of uninitialized value%s 
  (W uninitialized) An undefined value was used as if it were 
  already defined. It was interpreted as a "" or a 0,  but maybe
  it was a mistake. To suppress this warning assign a 
  defined value to your variables.