mpcp: 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/mpcp - from package: mpdtoys

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

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