my @student_info = ("001","John","002","Mary","003","Tom");
my %name_hash = @student_info;

my $grade_sth = $dbh->prepare("select id from grades where id = ? and grade = 'A'");

for my $student_id (sort keys %name_hash){
    $grade_sth->execute($student_id);
    my $student_name = $name_hash{$student_id};

    # do output here
}