Ditch that split

(254 strokes) Instead of split, $` and $' can be used.

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