Programatically configure SAML attributes using an iRule

I know I can use 'ACCESS::saml assertion' to send a completely custom assertion but I'd like to avoid it if possible.

Have a look at the attached screen shot for what I mean by multiple values. You are able to add multiple values to a single attribute so the resulting assertion will look something like the snippet below. So rather than adding a delimited string to a single value I want to split it out to multiple values but there doesn't seem to be a way to do that programmatically.

I hope that makes sense.

<saml2:AttributeStatement>
	<saml2:Attribute xmlns:saml2="urn:oasis:names:tc:SAML:2.0:assertion" Name="portalRole" NameFormat="urn:oasis:names:tc:SAML:2.0:attrname-format:unspecified">
		<saml2:AttributeValue xmlns:saml2="urn:oasis:names:tc:SAML:2.0:assertion">SM1</saml2:AttributeValue>
		<saml2:AttributeValue xmlns:saml2="urn:oasis:names:tc:SAML:2.0:assertion">SM2</saml2:AttributeValue>
	</saml2:Attribute>
</saml2:AttributeStatement>