\begin{pspicture}(0,0)(2,2)\showgrid
  \pscustom[fillstyle=solid,fillcolor=gray]{%
    \pscurve(0,.5)(1,1.5)(.9,1)
    \pscurve[liftpen=1](2,.5)(1,.1)(0,.1)}
\end{pspicture}
