+$usage = "Usage: $0 [-Dstring=replacement] [[infile] ...]\n";
+
+if (!defined(@ARGV)) { die ("$usage"); }
+
+# read in the command line and get some definitions
+while ($_=$ARGV[0], /^-/) {
+ if (/^-D/) {
+ # definition
+ shift(@ARGV);
+ if ( /-D(.*)=(.*)/ ) {
+ $def{"$1"}=$2;
+ } else {
+ die ("$usage$0: error in command line arguments.\n");
+ }
+ } else {
+ @cmd = split(//, $ARGV[0]); $opt = $cmd[1];
+ die ("$usage$0: unknown option '-$opt'\n");
+ }
+} # while parsing arguments
+
+if (!defined(%def)) {
+ die ("$0: nothing to do - no substitutions listed!\n");
+}