use strict;
  use warnings;
# I assume you have already established your database handle
  my $statement = "select my_key, my_value from my_table";
  my $ary_ref = $db_handle->selectcol_arrayref($statement, { Columns=>[1,2] });

  if ($DBI::errstr) {
    #do something
  }
  my %lookup_table = @$ary_ref if ref($ary_ref) eq 'ARRAY';