cpanp: 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 CentOS possible default full paths are:

/usr/bin/cpanp - from package: perl-CPANPLUS

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/cpanp - from package: libcpanplus-perl

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

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