my %options;
my $options->{'heredoc'} = '1';
my $config_copy = ReadINI ($copy,%options);
[download]

What this is actually saying is annotated below.

# Create a hash called %options
my %options;

# Create a *scalar* variable called $options and then try
# to use it as a reference.  Since it's just been created, 
# it's undefined.  Hence this won't work.
my $options->{'heredoc'} = '1';

# Call ReadINI passing it $copy and  your %options hash.
my $config_copy = ReadINI ($copy,%options);
[download]

I imagine that the line you want to have in the middle there is:

$options{heredoc} = 1;
[download]

It's a hash look up. %options is a hash, not a hash reference. If its not a reference, you don't want the arrow.

I hope this helps.