After an error, check that submit doesn't contain value="", because the browser won't display the default text label, "submit Query" or whatever.
value=""
To install HTML::FormFu, copy and paste the appropriate command in to your terminal.
cpanm
cpanm HTML::FormFu
CPAN shell
perl -MCPAN -e shell install HTML::FormFu
For more information on module installation, please visit the detailed CPAN module installation guide.