->fetchall_arrayref fetches all records so you don't need to loop (unless you don't have enough memory to fetch and return all the rows in one go.)

my $rows = $sth->fetchall_arrayref;
say Dumper $rows;
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Try fetching each row using ->fetchrow_arrayref.

#while (my $row = $sth->fetchall_arrayref) {
while (my $row = $sth->fetchrow_arrayref) {
   say Dumper $row;
}

poj