ZSH and GDBM support

I am trying to learn more about ZSH and the way that my shell is setup and operates. I am running OSX and have installed ZSH with HomeBrew so as not to use my standard system ZSH. However, before running brew install zsh, I ran brew info zsh and found that there are two build options which are confusing to me. 1. --with-gdbm-support While I can find information about _what_ GDBM is, I can't seem to find any practical applications or any reasoning about _why_ I'd want to support it. 2. --with-pcre-support I'm familiar with what PCRE stands for, but I guess I'm left wondering, does ZSH use a different regexp engine without this option? So again, I'm wondering why I'd want to add PCRE support. Any explanation of what these options would get me and why I'd want to use them would be much appreciated.