regex in ruby to convert from sample1.tex to sample2.tex ?

sample1.tex

\begin{enumerate}\setlength{\itemsep}{1pt}\setlength{\parskip}{0pt}\setlength{\parsep}{0pt}
\item
  item1
\item
  item2
\end{enumerate}

\begin{enumerate}\setlength{\itemsep}{1pt}\setlength{\parskip}{0pt}\setlength{\parsep}{0pt}
\item
  item1
\item
  item2
\end{enumerate}

\begin{itemize}\setlength{\itemsep}{1pt}\setlength{\parskip}{0pt}\setlength{\parsep}{0pt}
\item
  itemabc
\item
  itemabc
\end{itemize}

sample2.tex

\begin{enumerate}\setlength{\itemsep}{1pt}\setlength{\parskip}{0pt}\setlength{\parsep}{0pt}
\item
  item1
\item
  item2
\end{enumerate}

\begin{enumerate}\setlength{\itemsep}{1pt}\setlength{\parskip}{0pt}\setlength{\parsep}{0pt}
\item
  item1
\item
  item2
\end{enumerate}

\begin{itemize}\setlength{\itemsep}{1pt}\setlength{\parskip}{0pt}\setlength{\parsep}{0pt}
\item[*]
  itemabc
\item[*]
  itemabc
\end{itemize}

BEGIN {
RS = ""
FS = "\n"
}

$1 ~ /^\begin{itemize}/{
for (i=1; i<NF; i++)
{
if ($i == "\item")
print "\item[*]"
else
print $i
}
print ""
}

$1 !~ /^\begin{itemize}/{
print
print ""
}

$ awk -f tex.awk sample1.tex