p6.p6

replify ｢
  say 'Hello to your custom REPL! Type `say $a` to print the secret variable';
  my $a = "The value is {rand}";
｣;

sub replify (Str:D \pre-code = '') {
    use nqp;
    my %adverbs; # command line args like --MFoo
    my \r := REPL.new: nqp::getcomp('perl6'), %adverbs;
    my \enc := %adverbs<encoding>:v.Str;
    enc && enc ne 'fixed_8' && $*IN.set-encoding: enc;

    my $*CTXSAVE := r;
    my $*MAIN_CTX;
    pre-code and r.repl-eval: pre-code, $, :outer_ctx(nqp::getattr(r, REPL, '$!save_ctx')),
      |%adverbs;
    $*MAIN_CTX and nqp::bindattr(r, REPL, '$!save_ctx', $*MAIN_CTX);

    r.repl-loop: :interactive, |%adverbs;
}