Safe                     Unsafe
     ------------------------------------------
     foo                      foo bar
     -foo                     --foo
     foo_bar                  foo+bar
     jane3                    3jane

##</code><code>##

     my (%hash) = ( key_1 => 'value1', key_2 => 'value_2' );
     print $cgi->textfield(-name => 'input1');

##</code><code>##

     $hash{key_3} = 'value3';