What vendor? What software? Google turned up nothing definitive for 'reparg', so I guess it's a program used for whatever software we're not discussing. The rest are just arguments for the reparg program. %1 and %3 will resolve to values passed along the command line or values passed with a call.
! has no meaning in batch language, except in
set (XP, maybe 2K). !libname! might be the target of a global search and replace the user has to setup before running. Then again it could be anything.
Your manual would be the best source of information.
Good luck.