Q: Why is there no need to write SWITCHRC = "$HOME/.procmailrc"
A: Because "$HOME/.procmailrc" is already standing in line, waiting
for /etc/procmailrc to finish.
Not only that! If you write SWITCHRC = "$HOME/.procmailrc" and
somewhere in $HOME/.procmailrc or in a SWITCHRC called from it, the user
unsets SWITCHRC or sets it to /dev/null as an intentional quick exit
with a save to $DEFAULT, instead, procmail will go back to the start of
$HOME/.procmailrc. You'd be setting up an unexpected situation for the
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