if isdefined(Main, :Infiltrator)
  Main.infiltrate(@__MODULE__, Base.@locals, @__FILE__, @__LINE__)
end

julia> function f(x)
         out = []
         for i in x
           push!(out, 2i)
           @infiltrate
         end
         out
       end
f (generic function with 1 method)

julia> f([1,2,3])
Infiltrating f(x::Vector{Int64})
  at REPL[10]:5

infil> ?
  Code entered is evaluated in the current functions module. Note that you cannot change local
  variables, but can assign to globals in a permanent store module.

  The following commands are special cased:
    - `?`: Print this help text.
    - `@trace`: Print the current stack trace.
    - `@locals`: Print local variables. `@locals x y` only prints `x` and `y`.
    - `@exfiltrate`: Save all local variables into the store. `@exfiltrate x y` saves `x` and `y`;
      this variant can also exfiltrate variables defined in the `infil>` REPL.
    - `@toggle`: Toggle infiltrating at this `@infiltrate` spot (clear all with `Infiltrator.clear_disabled!()`).
    - `@continue`: Continue to the next infiltration point or exit (shortcut: Ctrl-D).
    - `@doc symbol`: Get help for `symbol` (same as in the normal Julia REPL).
    - `@exit`: Stop infiltrating for the remainder of this session and exit (on Julia versions prior to
      1.5 this needs to be manually cleared with `Infiltrator.end_session!()`).

infil> @locals
- out::Vector{Any} = Any[2]
- i::Int64 = 1
- x::Vector{Int64} = [1, 2, 3]

infil> 0//0
ERROR: ArgumentError: invalid rational: zero(Int64)//zero(Int64)
Stacktrace:
 [1] __throw_rational_argerror_zero(T::Type)
   @ Base ./rational.jl:32
 [2] Rational{Int64}(num::Int64, den::Int64)
   @ Base ./rational.jl:34
 [3] Rational
   @ ./rational.jl:39 [inlined]
 [4] //(n::Int64, d::Int64)
   @ Base ./rational.jl:62
 [5] top-level scope
   @ none:1

infil> @toggle
Disabled infiltration at this infiltration point.

infil> @toggle
Enabled infiltration at this infiltration point.

infil> @continue

Infiltrating f(x::Vector{Int64})
  at REPL[10]:5

infil> intermediate = copy(out)
2-element Vector{Any}:
 2
 4

infil> @exfiltrate intermediate x
Exfiltrating 2 local variables into the safehouse.

infil> @exit

3-element Vector{Any}:
 2
 4
 6

julia> safehouse.intermediate
2-element Vector{Any}:
 2
 4

julia> @withstore begin
         x = 23
         x .* intermediate
       end
2-element Vector{Int64}:
 46
 92