How to exclude text portions by simply setting a variable or option?

I'm writing a document where some text portions are confidential and would therefore like to create an environment (e.g. confidential) which I can then exclude from the PDF by simply setting a variable or option.

Is there any way of doing this in LaTeX, or better yet, is there a package for this?

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If you want to simply remove/skip such environments then Joseph's solution is the way to go. If you want to replace the text with something else, e.g. empty space, than have a look at Phantom and line break, which could be modified to not even draw the underlining. –  Martin Scharrer Sep 11 '11 at 10:16
Here are some attempts as solving this for inline or paragraph text that maintains the paragraph typesetting (hyphenation at line breaks - not supported by \phantom): Censor text spanning multiple lines. The soul package provided a good solution to tapping into the line breaking. –  Werner Sep 11 '11 at 14:24

You want the comment package. This provides the \includecomment and \excludecomment macros:

\documentclass{article}
\usepackage{comment}
\excludecomment{confidential}
\begin{document}
Some text

\begin{confidential}
Some secret text
\end{confidential}

\end{document}

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Nice, this works perfectly! Thanks! –  gablin Sep 11 '11 at 15:05
I ran into a problem where I got a lot of errors about too many }s or missing \endgroups and it took a while to find out how to fix it: How to fix issues with closing the commented out environment –  LarsNielsen May 5 '13 at 11:08