mwc.pl: 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/lib/ace/bin/mwc.pl - from package: mpc-ace

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

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