Execute SNUSP is an implementation of SNUSP.
Other implementations of SNUSP.
RCSNUSP
SNUSP
An implementation need only properly implement the Core SNUSP instructions ('$', '\', '/', '+', '-', '<', '>', ',', '.', '!', and '?'). Modular SNUSP ('#', '@') and Bloated SNUSP (':', ';', '%', and '&') are also allowed, but not required. Any extra characters that you implement should be noted in the description of your implementation. Any cell size is allowed, EOF support is optional, as is whether you have bounded or unbounded memory.

const echo2 =  raw"""
       /==!/======ECHO==,==.==#
       |   |
$==>==@/==@/==<==#"""
 
@enum Direction left up right down
 
function snusp(datalength, progstring)
    stack = Vector{Tuple{Int, Int, Direction}}()
    data = zeros(datalength)
    dp = ipx = ipy = 1
    direction = right    # default to go to right at beginning
 
    lines = split(progstring, "\n")
    lmax = maximum(map(length, lines))
    lines = map(x -> rpad(x, lmax), lines)
    for (y, li) in enumerate(lines)
        if (x = findfirst("\$", li)) != nothing
            (ipx, ipy) = (x[1], y)
        end
    end
 
    instruction = Dict([('>', ()-> dp += 1),
        ('<', ()-> (dp -= 1; if dp < 0 running = false end)), ('+', ()-> data[dp] += 1),
        ('-', ()-> data[dp] -= 1), (',', ()-> (data[dp] = read(stdin, UInt8))),
        ('.', ()->print(Char(data[dp]))),
        ('/', ()-> (d = Int(direction); d += (iseven(d) ? 3 : 5); direction = Direction(d % 4))),
        ('\\', ()-> (d = Int(direction); d += (iseven(d) ? 1 : -1); direction = Direction(d))),
        ('!', () -> ipnext()), ('?', ()-> if data[dp] == 0 ipnext() end),
        ('@', ()-> push!(stack, (ipx, ipy, direction))),
        ('#', ()-> if length(stack) > 0 (ipx, ipy, direction) = pop!(stack) end),
        ('\n', ()-> (running = false))])
 
    inboundsx(plus) = (plus ? (ipx < lmax) : (ipx > 1)) ? true : exit(data[dp])
    inboundsy(plus) = (plus ? (ipy < length(lines)) : (ipy > 1)) ? true : exit(data[dp])
    function ipnext()
        if direction == right && inboundsx(true)     ipx += 1
        elseif direction == left && inboundsx(false) ipx -= 1
        elseif direction == down && inboundsy(true)  ipy += 1
        elseif direction == up && inboundsy(false)   ipy -= 1
        end
    end
 
    running = true
    while running
        cmdcode = lines[ipy][ipx]
        if haskey(instruction, cmdcode)
            instruction[cmdcode]()
        end
        ipnext()
    end
    exit(data[dp])
end
 
snusp(100, echo2)