StringStartsQ¶ $ wo 'StringStartsQ["Hello World!", "Hello"]' True $ wo 'StringStartsQ["Hello World!", "Bye"]' False The one-argument operator form applies to a string later, e.g. inside Select. $ wo 'Select[{"CAC1", "CTG1", "ACT1", "CGA1", "CTC1"}, StringStartsQ["C"]]' {CAC1, CTG1, CGA1, CTC1}