\documentclass{article}

\usepackage{pst-node}

\setlength{\fboxrule}{0pt}
\setlength{\fboxsep}{2pt}

\begin{document}

\begin{pspicture}(2,2)
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  \pscurve[fillstyle=solid,fillcolor=red!30,linestyle=none](0,2)(1,1)(2,2)
  \psline(1,0)(1,0.7)
  \psline(1,1.2)(1,2)
  \rput(1,1){\Large\sffamily label}
\end{pspicture}

\makeatletter
\begin{pspicture}(2,2)
  \psframe[fillstyle=solid,fillcolor=blue!40,linestyle=none](0,0)(2,2)
  \pscurve[fillstyle=solid,fillcolor=red!30,linestyle=none](0,2)(1,1)(2,2)
  \rput(1,1){\psDefBoxNodes{label}{\fbox{\Large\sffamily label}}}
  \psclip{
    \pspolygon[linestyle=none]
      (\pst@dima,\pst@dimb)(\pst@dima,\pst@dimd)(\pst@dimc,\pst@dimd)(\pst@dimc,\pst@dimb)(\pst@dima,\pst@dimb)
      (label:bl)(label:br)(label:tr)(label:tl)
  }
    \psline(0,0)(2,2)
    \pscurve[linecolor=blue](1,0)(1.5,0.5)(0.5,1.5)(1,2)
  \endpsclip
\end{pspicture}

\end{document}