use CGI::Safe qw/ taint /;
    my $q = CGI::Safe->new;

##</code><code>##

    use CGI::Safe qw/ :standard taint /;

    my $var  = param( 'var' ) || '';
    ( $var ) = ( $var =~ /^([\s\w\d]+)$/ );

##</code><code>##

    use CGI::Safe;
    my $q = CGI::Safe->new;

    # set default tainted return to empty string
    $q->default_tainted( '' );

    # assign the regex
    $q->untaint( foo => qr/^([\w\s\d]+)$/ );

    # will return an empty string if it doesn't untaint
    my $foo = $q->param( 'foo' );

    if ( ! $foo )
    {
        error_routine( $q->tainted_param( 'foo' ) );
    }

##</code><code>##

    my $foo = param( { foo => qr/^([\w\s\d]+)$/ } );