use Data::Dumper;
my $dbg = 10; # set debug case no. or 0 for no case debugging
#...
$html_cvt_obj = new HTML::TextToHTML();

if ( $dbg == 10 ) {
    print STDERR Dumper( \$cfg::infile, \$html_file, \$html_cvt_obj );
    die "Aborting after fulfilling debug case no. 10\n";
}

$html_cvt_obj->txt2html(infile=>[$cfg::inv_file],
                        outfile=>$html_file,
                        explicit_headings=>1,
                        hrule_min=>20,
                        preformat_trigger_lines=>0,
                        );