my $sql= new SQL::Abstract( array_datatypes => 1 );

my $required = {  a => [1, 3, 5],  b => [2, 4, 6],};

my($stmt, @bind)= $sql->insert( testtable => $required );

##</code><code>##

stmt:  "INSERT INTO testtable ( a, b) VALUES ( ?, ? )"
@bind: (
          [
            1,
            3,
            5
          ],
          [
            2,
            4,
            6
          ]
        );

##</code><code>##

my $data = [
  {a => 1, b => 2},
  {a => 3, b => 4},
  {a => 5, b => 6},
];

##</code><code>##

# %columns will become the hash of arrays
my %columns;

# Foreach row of data collect its keys and create an empty array in %columns
$columns{$_} //= [] foreach map { keys %$_ } @$data;

# Then, for each row
foreach my $row ( @$data ) {
  # push the value foreach column
  push @{$columns{$_}}, $row->{$_} foreach keys %columns;
}