Likewise, you can pass a reference into a subroutine and use it without dereferencing:

%units = (miles => 6, stones => 11);  
fillerup( \%units );          # Pass in a reference
print $units{quarts};         # Prints 4

sub fillerup {
    local *hashsym = shift;   # Assign \%units to the typeglob
    $hashsym{quarts} = 4;     # Affects %units; no dereferencing needed!
}

These are tricky ways to pass around references cheaply when you don't want to have to explicitly dereference them. Note that both techniques only work with package variables; they would not have worked had we declared %units with my.