difference between attr= and attrs= ?

["Corisen" <csyap@starnet.gov.sg>]

hi,

may i know if there is any difference between using "attr=" and "attrs=" in
the ACL?

would really appreciate if someone could just spend a little time to explain
what is the entry in the "attr=attribute,entry" used for? when and why must
it be use in some cases for ACL to work properly.

thanks.