Might there be an error within PAR?

You'd have to consult PAR maintainers as to whether they consider it a error. I suspect that they'll say that you are using it wrongly.

When you package up your scripts with PAR, it not only incorporates your scripts and modules, but also as much of the installed perl--including any required DLLs--as is required to allow your script to run on a machine that does not have a perl installation. The intention being that you can distribute that single file to users and not require them to install Perl before using your code.

What you are attempting to do is run that packaged application on a system that already has a full perl installation. And a different version of Perl to that which was used during the packaging. Hence you are creating a situation whereby there are multiple executable files (dlls) with the same name but differing contents being loaded at runtime. Needless to say, this doesn't work.

Essentially, you have discovered that my guess regarding the presence of an incompatible version of perl510.dll exists within your .par file is correct. You now need to decide what to do about it. If you contact the PAR maintainers they might have a work-around?

The simplest solution would be for you to install the appropriate parts of your application--ie. just your sources files (.pls and .pms)--onto the system manually (by copying the files from the original system), and then, if necessary, repackage the application on the new system using PAR.