use CGI;
use HTML::Entities;
use URI::Escape;
my $q = CGI->new;

my $data;
my $toggle    = initToggle( 1 );

for my $ASCII ( 0 .. 255 ) {

    # The following is a hexadecimal list of characters that must be encoded
    # in query strings
    my $cgi_chars  = '\x00-\x29\x2b\x2c\x2f\x3a-\x40\x5b-\x5e\x60\x7b-\xff';

    # The following is a hexadecimal list of characters that often have their
    # HTML character code equivalent used instead of the characters themselves
    my $html_chars = '\x00-\x2f\x3a-\x40\x5b-\x5e\x60\x7b-\xff';

    my $char      = chr( $ASCII );                         # The actual character
    my $symbol    = encode_entities( $char, $html_chars ); # HTML code for Web page
    my $escaped   = uri_escape( $char, $cgi_chars );       # CGI representation
    my $html_code = encode_entities( $symbol );            # Re-encode HTML code so that it
                                                                # displays properly
    if ( $escaped eq '%20' ) { $escaped .= ' or +' };      # a space may be %20 or a +
    my @bgcolor   = ( '#FFFFFF', '#CCCCCC' );
    $data .= $q->Tr( { -align   => 'right',
                       -bgcolor => $bgcolor[ &$toggle ] },
                     $q->td( 
                             [ $ASCII < 33 ? '&nbsp;' : $symbol, $ASCII, $escaped, $html_code ] 
                           ) 
                   );
}

print $q->header,
      $q->start_html,
      $q->table( $data ),
      $q->end_html;

sub initToggle {
    my $limit = shift;
    my $count = 0;
    my $bit   = 0;
    unless ( $limit > 0 ) { die "initToggle() requires a positive argument\n" };
    return sub {
        $bit ^= 1 if $count++ % $limit == 0;
    }
}