# folder where the HTML-files (that need to be parsed are stored 
my $html_dir = '/path/to/dir/with/html.files';
# fetch  all.html-files from the directory 
my @html_files = File::Find::Rule->file->name( '*.html')->in( $html_dir);

for my $file ( @html_files ) {
    # parse the files
    # store all results  that you got from the HTML-files in only one txt-file.
}