use strict;
use warnings;

my $str="A: Gold, Black, Purple, Blue, Red     B: Black, Neon Pink, Neon Yellow, Neon Green, Neon Purple, Red, White, Neon Orange, Navy";

# create a hash using the A:, B: parts as keys and the following strings as values
my %str = grep  { $_ } 
          map   { s/^\s+//; s/\s+$//; $_; } 
          split /([A-Z]:)/, $str;


# iterate the hash and make the value strings to
# arrayrefs
for ( sort keys %str )
{
	$str{$_} = [ split /, /, $str{$_} ];
}

# output
for ( sort keys %str )
{
	print "Array $_ ", join (", ", @{$str{$_}}), "\n";
}