"Hello World!" EXCON Parser TCL Implementation

#!/usr/bin/tclsh

# http://esolangs.org/wiki/EXCON

# http://www2.tcl.tk/1591
proc bits2int {bits} {
     #returns integer equivalent of a bitlist
     set bits [format %032s [join $bits {}]]
     binary scan [binary format B* $bits] I1 x
     set x
}

# http://www.cab.u-szeged.hu/local/doc/tcl/Fragments.html#AscIntConv
proc asc i {
    if { $i<0 || $i>255 } { error "asc:Integer out of range 0-255" }
    return [format %c $i ]
}

set printf {}

puts "Welcome to the Quick and Dirty \"Hello World!\" EXCON parser."
puts "============================================"
puts "Default output is Binary."
puts "Type in 'int' for integer and 'ascii' for string."

if { $argc != 1 } {
    # no parameter
    # default to binary
    puts "Defaulting to binary print."
    set printf {b}
} else {
    set param [lindex $argv 0]

    if { [string eq $param {int}] } {
        puts "Printing as integer."
        set printf {i}
    } elseif { [string eq $param {ascii}] } {
        puts "Printing as ASCII."
        set printf {c}
    } else {
        puts "Unknown parameter.  Defaulting to binary."
        set printf {b}
    }
}

#H
lappend code {:<<<^<<<^!}
#e
lappend code {:^<<^<<<^<^!}
#l
lappend code {:<<^<^<<^<^!}
#l
lappend code {!}
#o
lappend code {:^<^<^<^<<^<^!}
# space
lappend code {:<<<<<^!}
#W
lappend code {:^<^<^<<^<<^!}
#o
lappend code {:^<^<^<^<<^<^!}
#r
lappend code {:<^<<<^<^<^!}
#l
lappend code {:<<^<^<<^<^!}
#d
lappend code {:<<^<<<^<^!}
# bang
lappend code {:^<<<<<^!}

# Clear buffer
for {set i 0} {$i < 8} {incr i} {
    set ar($i) 0
}

set llen [llength $code]
# Loop through instructions.
for {set ctr 0} {$ctr < $llen} {incr ctr} {
    set target [lindex $code $ctr]

    set len [string length $target]

    set needle 7

    for {set i 0} {$i < $len} {incr i} {
        set char [string index $target $i]

        switch $char {
            {:} {
                #reset the buffer.  do nothing.
                set reset 0
                for {set j 0} {$j < 8} {incr j} {
                    set ar($j) 0
                }
            }
            {^} {
                #flips the bit of the needle.
                set ar($needle) 1
            }
            {!} {
                set bits {}
                for {set j 0} {$j < 8} {incr j} {
                    append bits $ar($j)
                }

                # output.
                if { [string eq $printf {i}] } {
                    puts [bits2int $bits]
                } elseif { [string eq $printf {c}] } {
                    set int [bits2int $bits]
                    puts [asc $int]
                } else {
                    puts $bits
                }
            }
            {<} {
                 # move needle
                 set needle [expr "$needle - 1"]
            }
        }
    }

}

puts "Finished processing."