If it is really important, compile critical pieces into a C dll and call from Perl.
A C dll can be reversed also, but it takes more time.
If you need still more anti reversing built in, there are tools that can make reversing object code much harder. You can use those in conjunction with your C dll.
If it is really, really important for the reverser, they will reverse anything you do. You are just increasing the time and expense for them to reverse what you do.
At some point you have to consider whether the effort you put in anti reversing is more gainfully spent in adding features to your program
Reality:
Legal solutions are out of reach of most small businesses in USA.
No one gives a rat's ass about the legal notice you put on your program in large parts of the world.
Best wishes
Sanjay Mishra