print textfield(-name=>'first_name', -size=>'40', -maxlength=>'40', -d
+efault=>"$app{'first_name'}");
[download]

Whoo, why are you putting $app.. into quotes? Try

print textfield(
    -name => 'first_name', 
    -size => 40, 
    -maxlength => 40, 
    -default => $app{'first_name'},
);
[download]

Good Luck!