doctest.p6

#!/usr/bin/env perl6

# From Language/container.pod6:
sub lucky(::T $type) {
  my T $c-value; # closure variable
  return Proxy.new(
    FETCH => method () { $c-value },
    STORE => method (T $new-value) {
      X::OutOfRange.new(what => 'number', got => '13', range => '-∞..12, 14..∞').throw
      if $new-value == 13;
      $c-value = $new-value;
    }
  );
}

my Int $a := lucky(Int);
say $a = 12;    # OUTPUT: «12␤»
say $a = 'FOO'; # X::TypeCheck::Binding
say $a = 13;    # X::OutOfRange
CATCH { default { say .^name, ': ', .Str; say "Attempting to resume..."; if ! (.can('resumable') && .resumable) { .rethrow }; say "Resuming..."; .resume } };

# 12
# X::TypeCheck::Binding::Parameter: Type check failed in binding to parameter '$new-value'; expected Int but got Str ("FOO")
# Attempting to resume...
# This representation (VMException) does not support associative access (for type BOOTException)
#   in block  at /tmp/doctest.p6 line 19
#   in method <anon> at /tmp/doctest.p6 line 7
#   in block <unit> at /tmp/doctest.p6 line 17