use strict;
use Data::Dumper;

my %bits;
$bits{'zero'}='start element';
&loader('something',\%bits);
print 'Result:'.Dumper(\%bits);

sub loader{
 # loads values into hash..
 my $tail = shift;
 my %h_ref = %{+shift};
 
 print 'In sub:'.Dumper(\%h_ref);

 $h_ref{'one'}='thing_'.$tail;
 $h_ref{'two'}='thong_'.$tail;
 print 'After add:'.Dumper(\%h_ref);
}