my $security = XML::LibXSLT::Security->new();

    $security->register_callback( read_file  => sub {

        warn "read_file called in XML::LibXSLT";

        #i.e. when using the exsl:document() element or document() function (to read a XML file)

        my ($tctxt,$value) = @_;

        return 0;

    });

    $security->register_callback( write_file => sub {

        warn "write_file called in XML::LibXSLT";

        #i.e. when using the exsl:document element (or document() function?) (to write an output file of many possible types)

        #e.g.

        #<exsl:document href="file:///tmp/breached.txt">

        #   <xsl:text>breached!</xsl:text>

        #</exsl:document>

        my ($tctxt,$value) = @_;

        return 0;

    });

    $security->register_callback( read_net   => sub {

        warn "read_net called in XML::LibXSLT";

        #i.e. when using the document() function (to read XML from the network)

        #e.g. <xsl:copy-of select="document('http://localhost')" />

        my ($tctxt,$value) = @_;

        return 0;

    });

    $security->register_callback( write_net  => sub {

        warn "write_net called in XML::LibXSLT";

        #NOTE: it's unknown how one would invoke this, but covering our bases anyway

        my ($tctxt,$value) = @_;

        return 0;

    });

    $xslt->security_callbacks( $security );