#!/usr/bin/perl

sub mem {
    print "$_[0]:\n";
    system "/bin/ps", "-osize,vsize", $$;
}

sub foo {
    mem(0);
    my $data;
    $data .= "xxxxxxxxxx" for 1..1_000_000;
    mem(1);
    return \$data;  # return reference
}

my $r = foo();  # then get at the data using $$r
mem(2);

__END__
$ ./880173.pl
0:
   SZ    VSZ
  612  19804
1:
   SZ    VSZ
10468  29660
2:
   SZ    VSZ
10468  29660