use Akar::DBI::Statement qw(sql_param sql sql_param_inout); 
use Interpolation 'E' => 'eval', 
    'sqlp' => sub { return sql_param(@_) };

....

my $is_alive;
my $is_alive_sqlp = sql_param_inout( \$is_alive, 20 );
$this->db_Main->do(<<"END_PSQL");
    BEGIN
        if DBMS_SESSION.IS_SESSION_ALIVE(
           $sqlp{ $this->usessionid}
        ) 
        then
            $is_alive_sqlp := 1;
        else
            $is_alive_sqlp := 0;
        end if;
    END;
END_PSQL