weird interaction with `readline()`

the following code runs the loop "twice" and "in parallel" when smuggled into a repl
```julia
for k in 1:5
    @show k
    readline()
end
```

the output is as follows

```
julia> for k in 1:5
           @show k
           readline()
       end
k = 1
julia> for k in 1:5
           @show k
           readline()
       end
k = 1

k = 2

k = 2

k = 3

k = 3

k = 4

k = 4

k = 5

k = 5


julia> 
```
