Files passed to sed must be passed in the proper order.

Version 1 can be entered from the command line.

Version 2 can be made into an executable Unix shell script.

sed '/^end/,/^begin/d' file1 file2 ... fileX | uudecode   # vers. 1
sed '/^end/,/^begin/d' "$@" | uudecode                    # vers. 2