The filtering, '%{+elt1,elt2,elt3{subexpr}}' will evaluate subexpr
with a pattern only having the listed elements from the surrounding
pattern.
The deletion, '%{-elt1,elt2,elt3{subexpr}}' will evaluate subexpr
with a the surrounding pattern sans the listed elements.
Added -h instead of -?. And upon -h and --help, write usave to stdout
instead of stdin, and return 0 instead of 1.
-? still works like before as that's what getopt returns upon unknown
arguments.
Behdad Esfahbod