jlex: 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/jlex - from package: jlex

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