When you type #perl -V, you are executing the perl binary that the shell finds in your path. Different users have different paths depending on how they log in. This might be causing the strange behavior you are seeing.

The typical locations for the perl executable are /usr/bin and /usr/local/bin. You need to determine what the system is using and what your users are using and either install the proper perl binary in that system directory or symlink from /usr/bin/perl or /usr/local/bin/perl to the perl binary you want them to use.

If you want to keep both versions of perl on the system, install the new perl wherever you want (follow the suggestions above). Once you verify that it is working, just change the symlink /usr/bin/perl (or /usr/local/bin/perl) to point to the new perl binary. If something breaks, you can just switch the symlink back to the old version.

If you have a perl in several places, as it appears you do, it will save you some headaches to point them all at one actual binary. Otherwise, you'll need to maintain multiple versions of perl on your system and that can be painful.