# set one variable:
$t->param( some => 'value' );

# set a number of them
$t->param(
          one => 'value',
          two => 'value',
          three => 'value',
    );

# pass in an existing hash
$t->param( %lots_of_values );

# pass in a reference to a hash
$t->param( $ref_to_hash );