\usepackage {pstcol}
\begin{pspicture}(0,0)(2,1)\showgrid
\pscustom{%
\pscurve(0,.6)(1,.9)(2,.6)
\gsave
\pscurve[liftpen=1](2,.4)(1,.1)(0,.4)
\fill[fillstyle=solid,fillcolor=lightgray]
\grestore
}
\pscurve[liftpen=2](2,.4)(1,.1)(0,.4)
\end{pspicture}
Generated by dwww version 1.15 on Sat May 18 06:58:08 CEST 2024.