If you will try to compile nginx in Redhat Linux, you can get following error even if you have pcre-devel package installed:

Configuration summary + threads are not used + PCRE library is not found .... .... ./configure: error: the HTTP rewrite module requires the PCRE library. You can either disable the module by using --without-http_rewrite_module option, or install the PCRE library into the system, or build the PCRE library statically from the source with nginx by using --with-pcre= option.

If you are experiencing this small problem, you should simply use following parameter of configure script:

# ./configure --with-cc-opt="-I /usr/include/pcre"

And voila!

+ using system PCRE library

Now it can see and will use system PCRE library.