+# For example:
+#
+# % tracediff m5.opt --opt1 '--opt2|--opt3' --opt4
+# would compare these two runs:
+# m5.opt --opt1 --opt2 --opt4
+# m5.opt --opt1 --opt3 --opt4
+#
+# % tracediff 'path1|path2#/m5.opt' --opt1 --opt2
+# would compare these two runs:
+# path1/m5.opt --opt1 --opt2
+# path2/m5.opt --opt1 --opt2
+#
+# If you want to add arguments to one run only, just put a '|' in with
+# text only on one side ('--onlyOn1|'). You can do this with multiple
+# arguments together too ('|-a -b -c' adds three args to the second
+# run only).
+#
+# The '-n' argument to tracediff allows you to preview the two
+# generated command lines without running them.
+#
+
+use FindBin;
+
+$dryrun = 0;
+
+if (@ARGV >= 1 && $ARGV[0] eq '-n') {
+ $dryrun = 1;
+ shift @ARGV;
+}