gtml software package provides HTML pre-processor, you can install in your Debian 9 (Stretch) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install gtml
gtml is installed in your system.
Make ensure the gtml package were installed using the commands given below,
$ sudo dpkg-query -l | grep gtml *
You will get with gtml package name, version, architecture and description in a table
| Distro | Debian 9 stretch |
| Section | Web Software |
| Package | gtml |
| Version | 3.5.4-20 |
| Description | HTML pre-processor |
| Sub Section | Web |