mcxarray: 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/mcxarray - from package: mcl

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

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