%% 
%%  An UIT Edition example
%% 
%%  Example 04-20-1 on page 115.
%% 
%%  Copyright (C) 2012 Vo\ss 
%% 
%%  It may be distributed and/or modified under the conditions
%%  of the LaTeX Project Public License, either version 1.3
%%  of this license or (at your option) any later version.
%% 
%%  See http://www.latex-project.org/lppl.txt for details.
%% 

% Show page(s) 1

%% ==== 
\PassOptionsToClass{}{beamer}
\documentclass{exabeamer}
\AtBeginDocument{\Huge}% only for demo

%\StartShownPreambleCommands
\defbeamertemplate{list item}{rarrow}{$\rightarrow$}
\defbeamertemplate{list item}{Rarrow}{$\Rightarrow$}\setbeamertemplate{list item}[rarrow]{}
\newcounter{bcnt}
\newenvironment{bList}{\list{\usebeamertemplate{list item}}{\usecounter{bcnt}}}{\endlist}
%\StopShownPreambleCommands

\begin{document}
\begin{frame}{foo}{bar}
\begin{columns}[t]\begin{column}{0.3\textwidth}
\begin{bList} \item foo \item bar \end{bList}
\end{column} \setbeamertemplate{list item}[Rarrow]{}
\begin{column}{0.3\textwidth}
\begin{bList} \item foo \item bar \end{bList}
\end{column}
\addtobeamertemplate{list item}{\thebcnt: }{}
\begin{column}{0.3\textwidth}
\begin{bList} \item foo \item bar \end{bList}
\end{column}\end{columns}
\end{frame}
\end{document}