\documentclass{article}
\makeatletter
\newcommand{\fverb}{%
  \bgroup
  \def\verb@egroup{%
    \global\let\verb@balance@group\@empty\egroup\egroup}%
  \setbox0 =\hbox\bgroup\aftergroup\make@fverb\verb}
\newcommand{\make@fverb}{\fbox{\box0 }\egroup}
\makeatother
\begin{document}
\Huge  
\fverb|foo bar\/+^_|

\end{document} 
