Replacing a list with one variable

[Anonymous Monk]

Hi Monks,
Can you help a Perl novice please. I've searched the internet but can't find an answer or more likely don't know how to ask the right question.
I'm using a JSON request to get information from a remote server. The JSON request requires that I pass a method and a parameter to it. This is working as expected.
My problem is with formatting the parameter so that I can pass a list of varying size to it. This code works:

my $bookID1 = 'abc'
my $bookID2 = 'ghj'
my $bookID3 = 'zxc'
my $param = = {
                 IDs => [ $bookID1,$bookID2,$bookID3 ], 
                 sort => "AUTHOR",
                 maxResults => 100
              };

There can be a varying amount of bookIDs from 1 to 100, so I wish to build a list that I can then pass to $param.
For example,

my $bookIDList = "abc,ghj,zxc,bnm,qwe,rty,iop,sdf,ert";
my $param = = {
                 IDs => [ $bookIDList ], 
                 sort => "AUTHOR",
                 maxResults => 100
              };

This code above doesn't work. Any help or suggestions will be appreciated. Thanks
Tony