When I wrote,
| > Echo can also fail if the process lacks permission or opportunity to write
| > to stdout. A more reliable choice is true(1); its purpose in life is to do
| > nothing but exit with status 0.
Era Eriksson responded,
| (The command : is a shell builtin which always returns true status.
| Not exactly more readable than true(1), but if you need to have a slim
| .procmailrc, this will save you one process.)
"|| :" will save the invocation of true (unless true is built into $SHELL),
but procmail will still run a shell. On the other hand, as long as the
command itself has no characters from $SHELLMETAS, a weight of 1^1 and no
"|| anything" will avoid the shell process as well.