PREFIX : <http://example/>
PREFIX apf: <http://jena.hpl.hp.com/ARQ/property#>

SELECT *
{
  {  
    LET (?row := 1 )
    <http://example/ns#foo> apf:splitIRI (?ns1 ?ln1) .
    ?s1 ?p1 ?ln1 
  } UNION { 
    LET (?row := 2 )
    <http://example/ns#foo> apf:splitIRI (?ns2 ?ln2) .
    ?s2 ?p2 ?o2
  }
}