Since fabricate makes Python, a full language available, it's not that there's things that cannot be expressed, it's really about ease. So I'll tell you about something I did when I was a grad student.
I was using an up to date TeX install. My advisor wasn't. To placate him, I had to copy all of my packages, and all the packages they referred to, and so on down the line so that he could compile my papers. I did this entirely within make + some small shell scripts. The fact that I could write scanners for %.tex and %.sty and %.cls and have GNU make (obviously) automagically use them to build the dependency scripts I instructed it to include was immensely convenient. This is not impossible to do procedurally, but it was inconvenient, and the all-make solution had the attractive side that whenever there were bugfixes to the packages they got automatically included in what I was doing.
A better example, come to think of it, is the typical LaTeX woe; you can't build the final .dvi until you have accurate page numbers, references, tables of contents, indexes. You get all of those by--building the .dvi. So there's a strange circular dependency here. Make doesn't deal with this especially well, although it can be done. Ant and SCons don't even try.
I was using an up to date TeX install. My advisor wasn't. To placate him, I had to copy all of my packages, and all the packages they referred to, and so on down the line so that he could compile my papers. I did this entirely within make + some small shell scripts. The fact that I could write scanners for %.tex and %.sty and %.cls and have GNU make (obviously) automagically use them to build the dependency scripts I instructed it to include was immensely convenient. This is not impossible to do procedurally, but it was inconvenient, and the all-make solution had the attractive side that whenever there were bugfixes to the packages they got automatically included in what I was doing.
A better example, come to think of it, is the typical LaTeX woe; you can't build the final .dvi until you have accurate page numbers, references, tables of contents, indexes. You get all of those by--building the .dvi. So there's a strange circular dependency here. Make doesn't deal with this especially well, although it can be done. Ant and SCons don't even try.