You can use the -override parameter to force it to use the default value.

use strict;
use warnings;
use CGI qw/ :standard /;
 
print hidden(
       -name => "foo",
       -default => "bar",
   ), "\n";
   
print hidden(-name => "baz", -default => "bab" , -override => 1), "\n"
+;

__DATA__
C:\test>perl cgi.pl foo=test baz=test
<input type="hidden" name="foo" value="test" />
<input type="hidden" name="baz" value="bab" />

C:\test>perl cgi.pl
<input type="hidden" name="foo" value="bar" />
<input type="hidden" name="baz" value="bab" />
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