Configurator variant concatenate string

Hi, I would create a variable that is the result in user interface input

i created a new characteristic (CAS_description1) and assign to it a procedure to concatenate some value

but, I would concatenate only one character of a characteristic MODEL_UI.

in xls we use left() or Mid() or right, what is the correspondence in SAP statement?

$self.CAS_description1= $self.SERIES_UI || $self.MODEL_UI

if i do it in xls i could have

$self.CAS_description1= $self.SERIES_UI || left($self.MODEL_UI;1)

many thanks