It is one way to write a flip_flop, like in this snippet which uses a xor flip flop to alternate row colours in a 'pretty' HTML table...

sub pretty_table {
    my ($ary, $width, $no_center) = @_;
    my $header = shift @$ary;
    $width = $width ? qq!width="$width"! : '';
    my $html = qq!<table border="0" cellpadding="2" cellspacing="1" $w
+idth>\n!;
    my $cols = scalar @$header;
    $html .= get_row( $header, $cols, 'header' );
    my $flip_flop = 1;
    for my $row_ref ( @$ary ) {
        my $class = $flip_flop ? 'light' : 'dark';
        $html .= get_row( $row_ref, $cols, $class );


        $flip_flop ^= 1;


    }
    $html .= qq!  <tr>\n    <td  colspan="$cols" class="header">&nbsp;
+</td>\n  </tr>\n!;
    $html .= "</table>\n";
    $html = qq!<div align="center">\n<center>\n$html\n</center>\n</div
+>! unless $no_center;
  return $html
}

sub get_row {
    my ( $row_ref, $cols, $class ) = @_;
    my $html = qq!  <tr>\n!;
    for my $td ( 0.. $cols-1 ) {
        my $data = $row_ref->[$td] || '&nbsp;';
        $html .= qq!    <td  class="$class">$data</td>\n!;
    }
    $html .= "  </tr>\n";
  return $html;
}
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Of course you can get the same effect using $flip++ % 2 == 0 amongst others.

cheers

tachyon

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