mlpack_perceptron: 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/mlpack_perceptron - from package: mlpack-bin

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

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