my $bookparam;
if (defined $cgi->param("book")) {$bookparam = $cgi->param("book")}; 

##</code><code>##

[Sun Dec 11 22:03:35 2022] [error] [client ::1] Can't call method "param" on an undefined value at /Users/me/PERL/ScriptDir/dev.pl line 1026.