sub commit () {
    ($T || ${ caller() . '::T' })->commit;
    goto END_XACTION;
}

sub rollback () {
    ($T || ${ caller() . '::T' })->rollback;
    goto END_XACTION;
}

sub transaction (&) {
    my ($block) = @_;
    local $T = ${ caller() . '::T' } or croak "\$T not set";

    local $@;
    eval {
        $T->begin_work;
        $block->();
    };
    $@ ? rollback : commit;

    END_XACTION: die $@ . "commit not safe after errors, transaction rolled back"
        if $@;
}