apertium-rexlsx: command not found

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/apertium-rexlsx - from package: apertium

You may install the required package with command apt-get install {package}

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