Create a batchfile (.bat) that calls your script with the desired perl binary, eg.
C:\perl-5.8.0\bin\perl.exe myscript.pl.

You're probably already aware of this, but ActivePerl comes with a script called pl2bat which takes a perl script (*.pl) and creates a batch file (*.bat). The resulting file contains all your original source code along with a funky header that allows the script to be interpreted by both the Windows command shell and Perl.

One advantage of this system is that it ensures the command line arguments you provide to the batch file get passed to the Perl script.

You might need to edit the header code to make it explicitly call the version of Perl you want - I seem to recall it relies on the PATH environment variable.