My knowledge of Unix is far to old and out-of-date to be of any use with this. Does IE even run on unix platforms?

In any case, the description you have provided is far from clear. You give a very breif description a replicating bits of text from a browser window into another window as the mouse moves over the former, and you say you want to do this is perl. What is absent from your description is why you are trying to do this.

I am reminded of a project I was involved in a few years ago. It was a screen reader/speech synthesizer to allow vision impaired users to navigate/read a GUI desktop (the OS/2 Presentation Manager in that case). My contribution was adding the hooks into the guts of the OS to allow an add-on application to track the cursor and access the text beneath it. I can tell you that it required some highly optimised C/assembler code to make this happen in real time, and that was just tracking the cursor and text under it. The speech synthesis was performed by an external dedicated processor. Whilst processors are nearly a hundred times more powerful now, I still think that it is unlikely that it would be usuable if written in a partially interpreted language like perl even now.

If you provided a fuller explanation of what you are trying to achieve rather than what you think is the way to achieve it, you may well get some good suggestion from the wide range of able and willing unix guys assembled here.