weird_glitch

if I am to read a line from text file, I encounter the issue where it seems to detect % at range positions where, it doesn't exist...
ranges 23 25 27 29 don't hold the value % and so shouldn't trigger my switch case

<legend>%_frame_title_%</legend>
I can add a break clause, which I ultimately need to do, but still confusing to why is this switch triggering.

    mookie@cuddles:~/~scrap/~tcl $ tclsh hexScope.ix
    my line in base16: 3c6c6567656e643e255f6672616d655f7469746c655f253c2f6c6567656e643e
    my line in base32: <legend>%_frame_title_%</legend> 
    nothing found
    nothing found
    nothing found
    nothing found
    nothing found
    nothing found
    nothing found
    nothing found
    I found my % @ 8
    String is: %_frame_title_%</legend>
    Now lets see if the next character to see if it has _
    found _ 
    nothing found
    nothing found
    nothing found
    nothing found
    nothing found
    nothing found
    nothing found
    nothing found
    nothing found
    nothing found
    nothing found
    nothing found
    nothing found
    I found my % @ 22
    String is: %</legend>
    Now lets see if the next character to see if it has _
    _ not found
    What about my previous character, was that a _?
    indeed my previous character is a _ @ 21
    nothing found
    I found my % @ 24
    String is: /legend>
    Now lets see if the next character to see if it has _
    _ not found
    What about my previous character, was that a _?
    indeed my previous character is a _ @ 23
    nothing found
    I found my % @ 26
    String is: egend>
    Now lets see if the next character to see if it has _
    _ not found
    What about my previous character, was that a _?
    indeed my previous character is a _ @ 25
    nothing found
    I found my % @ 28
    String is: end>
    Now lets see if the next character to see if it has _
    _ not found
    What about my previous character, was that a _?
    indeed my previous character is a _ @ 27
    nothing found
    I found my % @ 30
    String is: d>
    Now lets see if the next character to see if it has _
    _ not found
    What about my previous character, was that a _?
    indeed my previous character is a _ @ 29
    nothing found
    >> 8 21 23 25 27 29


###### CODE #######

#     set myFile [open $base32_myFile]
#     set myFile [open "./timezone.craft"]
#     set lines [split [read $myFile] "\n"]
#     close $myFile

    set lines "<legend>%_frame_title_%</legend>"

    foreach line $lines {
    set x_pos 0
    set y_pos 1
    set z_pos 2
    set a_pos 3
    set list ""
    set located 0

    set i 0
    set string_length [string length $line]
                puts "\n"
                puts "my line in base16: [binary encode hex $line]"
                puts "my line in base32: $line "

    for {set z 0} {$z < $string_length} {incr z} {

        switch [binary encode hex [string range $line $x_pos $x_pos]] {
            25 { puts "I found my % @ $z"

                 switch $located {
                    0 {
                        lappend list $z
                    }
                 }

                 puts "String is: [string range $line $z end]"
                 puts "Now lets see if the next character to see if it has _"
                 incr i

                 switch [binary encode hex [string range $line $y_pos $y_pos]] {
                    5f {
                        puts "found _ "
                         incr x_pos
                         incr y_pos
                    }

                    default {
                        puts "_ not found"
                        puts "What about my previous character, was that a _?"
                        incr x_pos -1

                        switch [binary encode hex [string range $line $x_pos $x_pos]] {
                            5f {
                                puts "indeed my previous character is a _ @ [expr $z-1]"
                                lappend list [expr $z-1] ;# append the previous position

                            }
                            default {
                                puts "it was not"
                                incr x_pos 2
                                break
                            }
                        } ;# end switch
                    }
                } ;# end switch
            }

            default {
                puts "nothing found"
                incr x_pos
                incr y_pos
            }
        } ;# end switch
    incr i
  switch [string range $line $x_pos $y_pos] { "" { break } }
 }
    puts ">> $list"
} ;# end foreach