#!/usr/bin/perl -w
use strict ; use warnings ;

sub foo {
  my ($tag) = @_ ;
  print "$tag: ", wantarray ? "LIST" : "SCALAR", "\n" ;
  return wantarray ? ('a', 'b') : \78 ;
} ;

my $a = \foo('SCALAR \foo()') ;
my @a = \foo('LIST   \foo()') ;

my $b = ${foo('SCALAR ${foo()}')} ;
my @b = (${foo('LIST   ${foo()}')}) ;