I'm running on an old distrib where there is also something called sgml-tools that contains a lot of commands like docbook2*.

I remember once trying to hack the thing and find the perl stuff you probably speak about. The script itself is run at some point of the process to convert sgml docbook (not xml) to whatever. I remember also it was a rare piece of xxx.

I got a look at sourceforge, there is no longer a sgml-tools package there but in python and www.sgmltools.org is gone.

So if you thought it's what you want you may get the package from www.slackware.com, so, as a slackware package but it's just a tarball. Just browse the packages of old version.