...
my $sth = $dbh->prepare("{?=call some_procedure(?, ?, ?)}");
$sth->bind_param_inout(1, \$status, 20);
$sth->bind_param(2, $foo);
$sth->bind_param_inout(3, \$bar, 20);
$sth->bind_param_inout(4, \$baz, 20);
...