How to remove duplicate lines in file with TCL

i tested this code, but i dont know where is the probleme:

                            set in [open file.txt "r"]
            array set seen {}
            while {[gets $in line] != -1} {
                 blank lines should be printed as-is
                if {[string length [string trim $line]] == 0} {
                    puts $line
                    continue
                }

                 create the "key" for this line
                regsub {\mPoint \d+} $line {} key
                regsub {\mcolor=\w+} $key {} key

                 print the line only if the key is unique
                if { ! [info exists seen($key)]} {
                    puts $line
                    set seen($key) true
                }
            }
            close $in