COMMAND: exchange
ARGUMENTS: [combat mode] <item(s)> [extra info]  

The "exchange" command is a slightly different version of the "ready"  
command.  When you try to ready something with "exchange" that cannot be
readied because other items already occupy the slots required, "exchange"  
will attempt to unready any items that are in the way, then ready the new item.

For information on the arguments and usage of "exchange", see the help file for
the "ready" command.