"token fbc.bas" doesn't work as intended

#lang "fb"

'Token FBC.BAS" is supposed to scan a string for collisions with a list of dynamic length delimiters in the form of a token by index or otherwise the count of such.

#define  __DEBUG_TOKEN__

'Token fbc routines by Tim Keal & Mysoft

declare sub token_d(buffer as string, sep() as string, s() as long, byref o as long, byref d as long)

declare sub token_test()

declare function token overload (subject as string, sep() as string, index as string="1") as string

declare function token(subject as string, sep as string=",", index as string="1") as string

token_test()

sub token_test()

    dim as string subject, sep, index

    do

        input "subject:", subject

        if len(subject)=0 then
            subject="hello world!"
        end if
        print "subject:"; subject

        if subject = "exit" then exit do

        input "sep:", sep
        input "index:", index

        print "token:";token(subject, sep, index)
        print "---"

    loop

end sub

sub token_d(buffer as string, sep() as string, s() as long, byref o as long,byref d as long)

    dim as long n

    redim as long s(lbound(sep, 1) to ubound(sep, 1))

    for n = lbound(sep, 1) to ubound(sep, 1)
        s(n) = instr(1, buffer, sep(n))
    next n

    d = lbound(sep, 1)

    for n = lbound(sep, 1) to ubound(sep, 1)
        if s(n) < s(d) and s(n) > 0 then

            o = s(n)
            d = n

        end if
    next n

end sub


function token overload (subject as string, sep() as string, index as string="1") as string
    dim as string buffer, Ln, c, tok
    dim as long o, t, i, n, d
    dim as long s(lbound(sep, 1) to ubound(sep, 1))

    buffer = subject

    if index="ct" then
        i=0
    else
        i=val(index)
    end if

    o = len(buffer)+1

    select case i

    case is > 0

        t = 0

        do
            c = inkey : if c = chr(27) then exit do

            if len(buffer)=0 then exit do

            t = t + 1

            token_d buffer, sep(), s(), o, d

            Ln = left(buffer, o - 1)

            if o > 0 then
                Ln = left(buffer, o - 1)
            else
                Ln = buffer
            end if

            if o > len(buffer) then
                tok = buffer
                o = 0
                exit do
            end if

            if o > 0 then
                buffer = mid(buffer,o + len(sep(d)))
            else
                buffer = space(0)
            end if

            #ifdef  __DEBUG_TOKEN__
                print "t:";t;",o:";o;",sz:";len(buffer)
            #endif
            if (t = i) or (o = 0) or (len(buffer) = 0) then exit do

        loop until (t = i) or (o = 0) or (len(buffer) = 0)

        tok = Ln

    case is = 0

        t = 0

        do while o <> 0

            c = inkey : if c = chr(27) then exit do

            t = t + 1

            token_d buffer, sep(), s(), o, d

            if o > len(buffer) then
                tok = buffer
                o = 0
                exit do
            end if

            Ln = left(buffer, o - 1)

            #ifdef  __DEBUG_TOKEN__
                print Ln;",";
            #endif

            if o > 0 then
                buffer = mid(buffer,o + len(sep(d)))
            else
                buffer = space(0)
            end if

            #ifdef  __DEBUG_TOKEN__
                print "t:";t;",o:";o;",sz:";len(buffer)
            #endif
            if (o = 0) or (len(buffer) = 0) then exit do

        loop

        tok = str(t + 1)

    case else

        tok=space(0)

    end select

    #ifdef  __DEBUG_TOKEN__
        print "tok:";tok
    #endif

    token = tok

end function

function token(subject as string, sep as string=",", index as string="1") as string

  dim as string sTemp(0 to 0) : sTemp(0) = sep

  return token(subject, sTemp(), index)

end function