Zm9vYg==: foob
Zm9vYmE=: fooba
Zm9vYmFy: foobar
+Zm9vYg: foob
+Zm9vYmE: fooba
+Zm9v*Yg: foob
+:
+Znm=.is_base64? true
+Znm===.is_base64? false
+Z.sd=.is_base64? false
+Z==D.is_base64? false
+:
+Znm=: No error
+Znm===: Invalid padding length
+Z.sd=: Invalid Base64 character at position 1: .
+Z==D: Invalid padding character D at position 3