A subroutine can only return a scalar or a list. What the caller does with the result is completely out of the subroutine's control.

sub array {
  return 0 .. 5;
}

my %hash = array();
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However, you _could_ do something like the code below, but it's pretty strange stuff and I'm not sure how useful it is :-)

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

sub get_stuff {
  my $ref = shift;

  if (ref $ref) {
    if (ref $ref eq 'SCALAR') {
      $$ref = 'This is a scalar';
    } elsif (ref $ref eq 'ARRAY') {
      @$ref = qw(This is an array);
    } elsif (ref $ref eq 'HASH' ) {
      %$ref = (1 => 'This',
           2 => 'is',
           3 => 'a',
           4 => 'Hash');
    } else {
      die "Invalid reference type passed to get_stuff.\n";
    }
  } else {
    die "Non-reference passed to get_stuff.\n";
  }
}

my ($scalar, @array, %hash);

get_stuff(\$scalar);
get_stuff(\@array);
get_stuff(\%hash);

print "$scalar\n";
$"='|';
print "@array\n";
print map { $hash{$_} . ' ' } sort keys %hash;
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A subroutine may only know whether its caller wants a SCALAR or an ARRAY. The wantarray function handles this.

sub test {
  if (wantarray){
    return 'One String';
  } else {
    return ('A', 'List', 'of', 'Strings');
  }
}
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The DBI module uses a similar technique (non-relevant code removed for brevity):

sub fetchall_arrayref {
    my $slice= shift || [];
    my $mode = ref $slice;
    if ($mode eq 'ARRAY') {
        push @rows, [ @$row ] while($row = $sth->fetch);
    }
    elsif ($mode eq 'HASH') {
        push @rows, $row while ($row = $sth->fetchrow_hashref);
    }
    else { 
        Carp::croak("fetchall_arrayref($mode) invalid") 
    }
    return \@rows;
}
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  $sth->fetchall_arrayref( [] ) # returns Array references
  $sth->fetchall_arrayref( {} ) # returns Hash  references
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Cool stuff!

Russ