The CGI::Simple object is not the parameter but you’re treating it like it is–

perl -MCGI::Simple -E 'my $pass = CGI::Simple->new; $pass->param("pass
+"); say $pass'
CGI::Simple=HASH(0x7f8af5002ee8)
[download]

You want something more like–

my $cgi = CGI::Simple->new;
my $pass = $cgi->param("pass");
say $pass;
[download]