I need the first sentence of my captions to appear on its own line in a \large, bold font. I also need to same document to easily produce standard captions (all same font, no line breaks). I have implemented a class file that uses an option to directly modify \@caption and add the necessary formatting; however, my code isn't quite working. This example correctly places the first sentence of the caption on its own line in the correct font, but the text is not left-aligned.
\documentclass{article}
\usepackage{xstring}
\usepackage{etoolbox}
\usepackage{caption}
\captionsetup{labelfont=bf,labelsep=newline,tableposition=top}
\makeatletter
\newcommand\formatlabel[1]{%
\noexpandarg
\StrBefore{#1}{.}[\firstcaption] %
\StrBehind{#1}{.}[\secondcaption] %
\textbf{\large\firstcaption}
\\
\secondcaption}
\patchcmd{\@caption}{#3}{\formatlabel{#3}}
\makeatother
\begin{document}
\begin{table}
\centering
\caption{A Simple table. It has a caption with multiple sentences. It has a caption with multiple sentences. It has a caption with multiple sentences.}
\begin{tabular}{ l c r }
1 & 2 & 3 \\
4 & 5 & 6 \\
7 & 8 & 9 \\
\end{tabular}
\end{table}
\end{document}
\StrBefore{#1}{.}[\firstcaption] %and\StrBehind{#1}{.}[\secondcaption] %should fix the problem. – Guido Aug 03 '12 at 22:28