What about this, before parsing options using Getopt::Long, assuming the values will never have an ending ':' (untested):

@ARGV = map { s/^(.*):$/--$1/ if /:$/; $_ } @ARGV;
[download]

while (<@ARGV>) {
    my $arg = shift @ARGV;
    @options = split(/: /,$arg);
    print "XXXXXXXX\t", $options[$_], "\tXXXXXXXX";
}
[download]

If you have a space after the token, and your value is in quotes, the shell should separate them and put each one in a different item of ARGV.... it looks like you have that space, but I could be wrong.

Regardless, split takes an optional third argument which limits how many array items are returned. So put a 2 at the end of your split.

                - Ant
                - Some of my best work - (1 2 3)

$option_line = join ' ', @ARGV; #reconstitute
my @pairs = $option_line =~ m/(\w+:\s+\w+)/g; # grab option pairs
my %option;
for $pair (@pairs)
{
    # now split
    my ($name,$value) = split ":\s+", $pair, 2;
    # save each pair in hash
    $option{$name} = $value;
}
[download]

our %opt_hash; #can't use my
use Getopt::Declare;
my $spec = q{
    <name>: <value>    Name/Value pair
    { $::opt_hash{$name} = $value; }
    [repeatable]
};
# untested
[download]

Update: Missing $option_line corrected.

$option_line = join ' ', @ARGV; #reconstitute
my @pairs = m/(\w+:\s+\w+)/g; # grab option pairs
[download]

You missed matching against "$option_line" ...

my @pairs = ( $option_line =~ m/(\w+:\s+\w+)/g );
[download]