\begin{verbatim}
\begin{tabbing}
{\iden foobar\/}\xspa{1}{\iden a\/}\xspa{1}{\iden b\/}
    \xspa{1}$=$\xspa{1}{\iden c\/}\\
\skipover{{\iden foobar\/}\xspa{1}{\iden a\/}\xspa{1}
    {\iden b\/}\xspa{1}}{\keyword where\/}\\
\skipover{{\iden foobar\/}\xspa{1}{\iden a\/}\xspa{1}
    {\iden b\/}\xspa{1}{\keyword wher\/}}{\iden c\/}
    \xspa{1}$=$\xspa{1}{\iden a\/}\xspa{1}$+$\xspa{1}
    {\iden b\/}
\end{tabbing}
\end{verbatim}