I would suggest probing carefully, but diplomatically, to better understand what sort of criteria the client’s Architectural Council would be using to make their decision. I would presume, as should you, that the council is quite aware of the Perl language (and that it works well) ... so, when they ask for a “business” case that Perl is “suitable,” I would endeavor to better understand what other technologies they are using right now, how they deploy software assets (and to what machines), what interoperability is required, and, well, “does it hurt / where does it hurt” right now. Adding any new software development technology to “the mix” is always risky and costly. You don’t need to proselytize for the Perl language. Rather, you need to present a business case, within the specific business context of this client, that, for this client, there is: a business benefit; acceptable business risk; return on investment (ROI); and a truly compelling reason to add something new, instead of doing the work with the existing tools already in use there. Leave the pom-poms at home.