listings wrong syntax highlighting in perl - format specification

Perl uses '#' as an introduction for a comment, but also as a format specification. This produces problems in the syntax highlighting in the listings-package. How can I fix it?

\documentclass{article}
\usepackage{listings}
\usepackage{xcolor}
\begin{document}
\begin{lstlisting}
#this is a comment
my $n=89; #the "@###.####" is NOT a comment format OUT= @###.#####$n
.
\end{lstlisting}
\end{document}

-

\documentclass{article}
\usepackage{listings}
\usepackage{xcolor}
\begin{document}

my $n=89; #the "@###.####" is NOT a comment format OUT= @###.#####$n