Value passing between Perl and LaTeX in PerlTeX

example-perltex.tex

\documentclass{article}
\usepackage{perltex}
\begin{document}

\perldo{
  $pvalue = 5;
}
\newcounter{tvalue}
\setcounter{tvalue}{6}

\perlnewcommand{\addtopvalue}[1]{
  $pvalue += $_[0]; return;
}
\addtocounter{tvalue}{1}
\addtopvalue{1}

\perlnewcommand{\magnifypvalue}[1]{
  $pvalue *= $_[0];
  return "\\setcounter{tvalue}{$pvalue}";
}
\magnifypvalue{\arabic{tvalue}}
The answer is \arabic{tvalue}.

\end{document}