I tested sci-biology/perlprimer on x86, so please, add x86 keyword.
I added keyword but there is dependency missing where the ebuild will be tricky to be written: See under source installation http://perlprimer.sourceforge.net/download.html http://www.ncbi.nlm.nih.gov/spidey/spideysource.html
File is already keyworded for ~x86: see https://github.com/gentoo/sci/blob/master/sci-biology/perlprimer/perlprimer-1.1.21.ebuild