diff --git a/b2/boom.c b/b2/boom.c
index 94e384c..83ea06e 100644
--- a/b2/boom.c
+++ b/b2/boom.c
@@ -18,9 +18,11 @@
 #include "lang.h"
 #include "param.h"
 #include "subex.h"
+#include "db.h"
 
 
 static struct param *vars = NULL, **last_var = &vars;
+static int select_parts = 0;
 
 
 static void add_var(const char *arg)
@@ -44,14 +46,26 @@ static void do_substitutions(void)
 {
 	struct param *out;
 	const struct param *var;
+	const struct part **parts, **p;
 
 	out = substitute(substitutions, vars);
-	for (var = out; var; var = var->next) {
-		printf("%s", var->u.name);
-		dump_relop(stdout, var->op);
-		printf("%s\n", var->value.u.s);
+	if (select_parts) {
+		parts = select_parametric(out, &hierarchy);
+		if (!parts) {
+			fprintf(stderr, "no matches\n");
+		} else {
+			for (p = parts; *p; p++)
+				printf("%s %s\n", (*p)->domain, (*p)->name);
+			free(parts);
+		}
+	} else {
+		for (var = out; var; var = var->next) {
+			printf("%s", var->u.name);
+			dump_relop(stdout, var->op);
+			printf("%s\n", var->value.u.s);
+		}
+		free_vars(out);
 	}
-	free_vars(out);
 }
 
 
@@ -66,6 +80,7 @@ static void usage(const char *name)
 "  -p  providers\n"
 "  -s  substitutions\n"
 "  -q var=value ...\n"
+"  -Q var=value ...\n"
     , name);
 	exit(1);
 }
@@ -90,7 +105,10 @@ int main(int argc, char **argv)
 				process = parse_substitutions;
 			else if (!strcmp(argv[i], "-q"))
 				process = add_var;
-			else
+			else if (!strcmp(argv[i], "-Q")) {
+				process = add_var;
+				select_parts = 1;
+			} else
 				usage(*argv);
 		} else {
 			process(argv[i]);