Alright, since you are using the function oriented interface, you need to import the :cgi-lib set of function calls, to use the Vars() function, which will return the params as a hash, multivalued fields being delimited by a "\0" (null) character.

use CGI qw(:cgi-lib);
%params = Vars();

foreach $member (key %params) {
    print "$member = ";
    @values = split /\0/, $params{$member};
    print "@values\n";
    
}
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Cheers,
Erik