flex-old software package provides Old version of the fast lexical analyzer generator, you can install in your Debian 8 (Jessie) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install flex-old
flex-old is installed in your system.
Make ensure the flex-old package were installed using the commands given below,
$ sudo dpkg-query -l | grep flex-old *
You will get with flex-old package name, version, architecture and description in a table
| Distro | Debian 8 jessie |
| Section | Development |
| Package | flex-old |
| Version | 2.5.4a-10 |
| Description | Old version of the fast lexical analyzer generator |
| Sub Section | Devel |