Perl 6: Invoke a REPL in the context of the caller (debugging tool)

example.p6

#!/usr/bin/perl6

use Debug::REPLHere;
sub f { my $secret = 42; repl-here; say "The secret is $secret"; }
f

# Example session:
# $ ./example.p6
# > $secret
# 42
# > $secret=5
# 5
# > ^D
# The secret is 5

REPLHere.pm6

unit package Debug::REPLHere;

use nqp;

our sub repl-here($context=Nil) is export {
    my $comp = nqp::getcomp('perl6');
    my $repl = REPL.new($comp, {});
    my $nqpctx := nqp::getattr(nqp::decont($context // CALLER::), PseudoStash, '$!ctx');
    $repl.^attributes.first('$!save_ctx').set_value($repl, $nqpctx);
    $repl.repl-loop;
}