Filters 2

$ cat filter2.tcl                                                                                                        
# Filters 2

package require tov

set o [[::tov::FileReader new in.txt] cascade {
      receiver [[::tov::FilterDoer new] cascade ^ {
          tocalc {string toupper $value}
        ^ receiver [[::tov::FilterDoer new] cascade ~ {
              tocalc {regsub -all I $value A}
            ~ receiver [[::tov::FileWriter new out.txt] cascade , {
                  configure -buffering none
                , yourself
              }]
            ~ yourself
          }]
        ^ yourself
      }]
    ` value -1
    ` yourself
}]


# EOF


$ cat in.txt;rm -f out.txt;tclsh8.6 filter2.tcl;cat out.txt  
A Tcl script is a string containing one or more commands.
A TCL SCRAPT AS A STRANG CONTAANANG ONE OR MORE COMMANDS.