Any PowerShell script for this please? Iterating through sites/lists/libraries/items etc. and granting permissions in this way

Hi there

I have a CSV file which looks like this:

Domain1\Tom, Domain2\Tom
Domain1\Dick, Domain2\Dick
Domain1\Harry, Domain2\Harry

Desired function of script:

If Domain1\Tom has READ permission in SPList XYZ - the script should grant Domain2\Tom READ permissions in the same list and so on. 
Script should iterate through entire web application and do this for every list/library/item/spweb/spsite etc.

Greatly appreciated.

Thanks so much.