mllex: command not found

Have You tried accessing the binary with the full path?

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/mllex - from package: mlton-tools

You may install the required package with command apt-get install {package}
Error in other languages:
mllex: bevel nie gevind nie
mllex: comandă negăsită
mllex: comando não encontrado
mllex: commande introuvable
mllex: command not found
mllex: käsku ei ole
mllex: không tìm thấy lệnh
mllex: komanda nerasta
mllex: Kommando nicht gefunden.
mllex: kommandot finns inte
mllex: komut yok
mllex: nie znaleziono polecenia
mllex: níor aimsíodh an t-ordú
mllex: no se encontró la orden
mllex: no s'ha trobat l'ordre
mllex: opdracht niet gevonden
mllex: parancs nem található
mllex: perintah tidak ditemukan
mllex: príkaz nenájdený
mllex: příkaz nenalezen
mllex: команда не найдена
mllex: командата не е открита
mllex: 命令找不到
mllex: コマンドが見つかりません