my %hash = (
    one => 1,
    two => 2,
);

foo(%hash);

sub foo {
   print join(' | ', @_), "\n";
}

##</code><code>##

sub foo {
    my %hash = @_;
}

# works fine
foo(%hash);

# uh oh
foo('nameofhash', %hash);

# not good at all
foo(@names, %hash);

##</code><code>##

# pass a reference to %hash, which is a scalar
foo(\%hash);

sub foo {
    my $hashref = shift;
}

##</code><code>##

sub foo {
    my $hashref = shift;
    # add data
    bar($hashref);
}

sub bar {
    my $hashref = shift;
    # manipulate data as above
}