perl 5.24.1 is the current stable release, for your information, and is available for Unix/Linux, and for Windows ActiveState and Strawberry.
Bureaucracy is completely understandable by most here (I'm sure), so I might advise to test things on more recent versions (after taking all the advice provided into consideration) on the side, and if results are improved, you have justification to request a change. That, combined with the fine documentation on each release perldoc perldelta, may help show that allowing newer releases is pretty reasonable.
I just went through this with a $work client, and my job is designing solutions for a significant C++ suite with Python hooks. I wanted Perl because I can debug and write quick tests for a Python script that accesses the underlying C++ dll quicker than I could by using Python directly. Client uses Perl for a few things, but they mandated v5.8.8. That changed pretty quickly, in this 290k+ user environment after I demo'd a couple of quick things that used Perl to aggrivate Python to access what I needed done.