If you copy over the normal installation file, you should be able to install without any access to the internet. Adding additional modules can be more tricky.
An alternative would be to download the portable version of Strawberry Perl, which is used by running a batch file that launches a command prompt and sets the environment variables for that new command prompt with the information needed to use the portable Strawberry Perl. If you use this on the system that has access to both the internet and the isolated system, you can use that system to install additional modules and the copy over the additional files to the isolated system. (Or zip up the whole thing, send that over to the isolated system and then unzip it. Which ever method that you find more convenient to use.)
If you have physical access to the isolated system, you can also put portable Strawberry Perl on a USB stick drive. Then you just move the stick drive to a system with internet access to install new modules when needed and move it back.