oops, that also matches 'Egon sees |.' so that should have been:

'Egon sees Erna.' readStream
 match:[ :i | i matchOneOf: #('Egon' 'Erna' 'Emma') action:[:subj|subj]]
 and: $ 
 and: 'sees'
 and: $ 
 and: [: i | i matchOneOf: #('Egon' 'Erna' 'Edna') action:[:obj|obj]]
 and: $.
 action: [ : sentence | sentence]