add some comments

post-processing/z-every-line.pl

@@ -4,18 +4,20 @@
 
 my $z = 0;
 
+# read stdin and any/all files passed as parameters one line at a time
 for (<>) {
-	if (/Z(\d+(\.\d+)?)/) {
-		$z = $1;
-		print;
+	# if we find a Z word, save it
+	$z = $1 if /Z(\d+(\.\d+)?)/;
+
+	# if we don't have Z, but we do have X and Y
+	if (!/Z/ && /X/ && /Y/ && $z > 0) {
+		# chop off the end of the line (incl. comments), saving chopped section in $1
+		s/\s*([\r\n\;\(].*)//s;
+		# print start of line, insert our Z value then re-add the chopped end of line
+		print "$_ Z$z $1";
 	}
 	else {
-		if (!/Z/ && /X/ && /Y/ && $z > 0) {
-			s/\s*([\r\n\;\(].*)//gs;
-			print "$_ Z$z $1";
-		}
-		else {
-			print;
-		}
+		# nothing interesting, print line as-is
+		print;
 	}
 }