One of the first lines of the docs is "FETCHING THE NAMES OF ALL THE PARAMETERS PASSED TO YOUR SCRIPT". Once you know the name of the parameters, you can use them for "FETCHING THE VALUE OR VALUES OF A SINGLE NAMED PARAMETER".

use CGI qw( escapeHTML );

my $cgi = CGI->new();

foreach my $param ($cgi->param()) {
   foreach my $value ($cgi->param($param)) {
      printf("<div>%s = %s</div>\n",
         escapeHTML($param),
         escapeHTML($value),
      );
   }
}
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