diff --git a/src/replace.🗿 b/src/replace.🗿
new file mode 100644
index 0000000..fa69170
--- /dev/null
+++ b/src/replace.🗿
@@ -0,0 +1,15 @@
+replace(str, fill, start, stop)
+{
+	local out;
+	local sum;
+
+	out = galloc(strlen(str) + strlen(fill) - (stop - start) + 1);
+	if (out == NULL)
+		return (NULL);
+	strncpy(out, str, start);
+	strncpy(out + start, fill, strlen(fill));
+	sum = start + strlen(fill);
+	strncpy(out + sum, str + stop, strlen(str) - stop);
+	[out + sum + strlen(str) - stop] = 0;
+	return (out);
+}
diff --git a/tests/replace.🗿 b/tests/replace.🗿
new file mode 100644
index 0000000..6651487
--- /dev/null
+++ b/tests/replace.🗿
@@ -0,0 +1,9 @@
+main()
+{
+	name = "replace";
+
+	test_str(replace("yo ca va ?", "t", 2, 3), "yotca va ?", "");
+	test_str(replace("yo ca va ?", "", 2, 3), "yoca va ?", "empty fill");
+	test_str(replace("yo ca va ?", "aaaaa", 2, 3), "yoaaaaaca va ?", "");
+	test_str(replace("", "aaaaa", 0, 0), "aaaaa", "");
+}