diff --git a/vala/regexp/ex.vala b/vala/regexp/ex.vala
index d14b647..1b69bc8 100644
--- a/vala/regexp/ex.vala
+++ b/vala/regexp/ex.vala
@@ -1,3 +1,9 @@
+/*The following trailing characters can be used:
+ *  i, letters in the pattern match both upper- and lowercase letters
+ *  m, the "start of line" and "end of line" constructs match immediately following or immediately before any newline in the string, respectively, as well as at the very start and end.
+ *  s, a dot metacharater . in the pattern matches all characters, including newlines. Without it, newlines are excluded.
+ *  x, whitespace data characters in the pattern are totally ignored except when escaped or inside a character class. 
+ */
 bool is_valid_email(string email) {
 	var status = true;
 	stdout.puts(@"$email is ");