The problem is that the expensive POS software doesn´t run on Centos because the perl version Centos uses is too old.
Life is a compromise. If the expensive POS software isn't designed to run on RHEL/CentOS then you will need to run it on a different OS. I know your desire is to keep everything the same, but that's the compromise.
Since there is a recent perl version available, there has to be some way to use it.
No doubt there is - but the compromise is the amount of work necessary to get it functioning in a satisfactory and stable way.
I wonder if you might be better of using something like Fedora since it's relatively close in structure to CentOS - it really depends on how many machines you need to support and if the 6 month upgrade cycle is going to be too onerous. If nothing else it might tide you over until RHEL 8 - which might well be based on Fedora 26 or 27 if you look at other upgrade cycles.
P.