I want to pass a macro to a `showgrid` key. The macro can be redefined later. Its possible values are `top`, `bottom`, `false`, `true`.

The following MWE produces a blank page. How to fix it?

```
\documentclass[border=12pt,pstricks]{standalone}
\usepackage{pstricks}

\def\status{true}

\begin{document}

\begin{pspicture}[showgrid=\status](3,3)
\end{pspicture}

\end{document}

```