Correct. You can use libraries in Perl (autobox and a class offering "join") so you can write it in Perl as:

   $foo->{bar}->join(',')

I've done that in FunctionalPerl[1]:

  use FunctionalPerl ":autobox";
  my $foo= {bar=> ["hi", "there"]};
  is $foo->{bar}->join(','),
     'hi,there';

[1] https://metacpan.org/pod/FunctionalPerl