Regex to extract citations and other parenthetical expressions from text

Print out parenthetical expressions using sed:
sed 's/(/\n(/g' InputFile.txt | sed 's/)/)\n/g' | grep "^(";

Remove parenthetical expressions using perl: 
perl -pe 's|(\(.*?\))||g' InputFile.txt;

Homebrew, Mac OS 10.11, Xcode 8, Clang, and the problem with thread_local

The version of the clang compiler that comes with Xcode 7 does not recognize the thread_local keyword.  Packages installed with Homebrew that use certain c++11 or higher commands may terminate during compilation with errors like "thread-local storage is not supported for the current target".  Xcode 8, which contains a suitable clang, cannot be run on MacOS 10.11.  Catch-22.

To work around, install a new version of gcc using Homebrew:

brew install gcc;

Now figure out which version of gcc was installed by Homebrew:

brew list gcc;

If gcc 8 was installed you will see something like: /usr/local/Cellar/gcc/8.2.0/bin/gcc-8
in the list of brew-installed gcc programs.  Now, tell Homebrew to use this newer version of gcc, instead of the old version of clang from xcode, to install your program.  As an example, I use the package poppler:

brew install --cc=gcc-8 poppler;