When attempting to build PerlMagick-4.29 on a RH 6.1 system, the include file magick/defines.h was not found. I believe this file should have been part of the ImageMagick-devel package. I solved the build problem by downloading the ImageMagick-4.2.9 tar ball and copying magick/defines.h to the /usr/X11R6/include/X11/magick directory. The ImageMagick tar ball I used was downloaded from http://www.wizards.dupont.com/cristy/ImageMagick.html
The defines.h file is specifically tagged to not be included in an installation by the ImageMagick team. PerlMagick is also included with current versions of ImageMagick.