sub myfunc {
    my $href = shift; 
    print $href->{foo}, "\n";
}

my %h = ( foo => 'bar' );

myfunc(\%h);

##</code><code>##

sub myfunc {
    my %hash = @_; 
    print $hash{foo}, "\n";
}
my %h = ( foo => 'bar' );
myfunc(%hash);
myfunc( foo => 'baz' );