\documentclass[12pt,a4paper]{article} % Herbert Voss 2004-05-05
\usepackage{pstricks}
\xdefinecolor{lightred}{rgb}{1.0, 0.8, 0.8}
\newsavebox\pstBox
\newlength\pstWidth
\newlength\pstHeight
\makeatletter
\def\psLBox{\@ifnextchar[{\psLBox@i}{\psLBox[]}}
\def\psLBox@i[#1]#2{%
  \psset{linearc=0.4,shadow=true,shadowsize=0.2,%
      fillstyle=solid,fillcolor=white}
  \ifx#1\empty\else\psset{#1}\fi
  \sbox\pstBox{#2}
  \pstWidth=\wd\pstBox
  \pstHeight=\ht\pstBox
  \advance\pstHeight by \dp\pstBox
  \advance\pstHeight by \pslinearc
  \advance\pstWidth by \pslinearc
  \begin{pspicture}(\pstWidth,\pstHeight)
    \psline(\pstWidth,0)(0,0)(0,\pstHeight)(\pstWidth,\pstHeight)%
    \psline[shadow=false](\pstWidth,\pstHeight)(\pstWidth,0)
    \rput(0.5\pstWidth,0.5\pstHeight){#2}
  \end{pspicture}
}
\makeatother
\begin{document}

\psLBox[fillcolor=lightred]{Some text in a box}% 
\psLBox[fillcolor=yellow]{%
\parbox{3cm}{Some text in a box with line arcs only 
    on the left side}
}% 
\end{document}

