Either tt(NOTRANS) or tt(txtcommand) can be used to send txt commands to the
output. 

E.g., the following code sends a TXT command tt(<hr>) to the output file when 
in TXT mode:
        verb(\
    COMMENT(-- alternative 1, using txtcommand --)
    txtcommand(<hr>)
    
    COMMENT(-- alternative 2, using NOTRANS --)
    IFDEF(txt)(
        NOTRANS(<hr>)
    )()
        )
