#! perl -wspi.bak
BEGIN{
	die <<USAGE unless defined($domain) & $domain ne '1'  && defined($name) & $name ne '1';
	Usage: $0 -spi -name=fred --domain=some.com path/to/userfile

USAGE
	my ($started, $finished) = (0,0);
}
next if $finished;					     # Just print the rest once we've done the biz
$started = /^$domain/o 					# look for the start of the right block
	or next unless $started;				# and just print till we find it
$finished = !/$domain/o					# Continue just printing till we find the end
	or next unless $finished;
print "$name\@$domain\t$name\n";		      # Then print the new bit
END{
	 	unlink $main::ARGV . $^I
	 or	warn "Failed to delete backup $main::ARGV$^I; $!\n"
}