Joining multiple files with different prefix for each

[spmundi]

When joining multiple files "..join ... file1.csv file2.csv ..' there is no capability to have the fields in the joined files be given a prefix where the prefix depends on the joined file. ie I may want prefix1_ for file1.csv, prefix_2 for file2.csv ...etc.
If the option --rl were to allow a comma separated list, it would solve this problem.
If the number of values in --rl were fewer in number than the count of joined files
then the last member -f --rl could be used for all the remaining files.

This is not, it almost goes without saying, an especially important enhancement, but I would have found it useful in some recent analysis