Here's the game plan: Copy ALL of the perl scripts you wish to convert into a new directory. Convert and test throughly test each script (though less thoroughly than you did before since now you have the benefits of strict and warnings, right?). You'll know then when you're done, you can copy and overwrite those old scripts.
Typical pitfalls of conversion- remember:
predeclare your variables
keep the rules of strict references (good programming usually implies this)