In the special case where I have a select statement that will return key/value pairs, I usually use this syntax:

  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';
[download]

This has the happy result of creating a reference to an array which can be treated as a series of key/value pairs, and thus can directly populate my hash table. I think it is a nice, readable shortcut.