Invert any if/unless

#!perl -nl
sub maybe_print_m {
	$DONE_M || print "$PREFIX.M";
}
$PRINTED_LINE = 1;
unless (/$PREFIX/) {
	maybe_print_m;
	$DONE_M = 0;
}
($PREFIX, $s) = split /\./, $_, 2;
if (/[M-Z]$/) { 
	maybe_print_m unless /M$/;
	$DONE_M = 1;
}
print;
END {
	$PRINTED_LINE&&maybe_print_m
}