cpan-outdated: command not found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/usr/bin/cpan-outdated - from package: cpanoutdated

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

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cpan-outdated: bevel nie gevind nie
cpan-outdated: comandă negăsită
cpan-outdated: comando não encontrado
cpan-outdated: commande introuvable
cpan-outdated: command not found
cpan-outdated: käsku ei ole
cpan-outdated: không tìm thấy lệnh
cpan-outdated: komanda nerasta
cpan-outdated: Kommando nicht gefunden.
cpan-outdated: kommandot finns inte
cpan-outdated: komut yok
cpan-outdated: nie znaleziono polecenia
cpan-outdated: níor aimsíodh an t-ordú
cpan-outdated: no se encontró la orden
cpan-outdated: no s'ha trobat l'ordre
cpan-outdated: opdracht niet gevonden
cpan-outdated: parancs nem található
cpan-outdated: perintah tidak ditemukan
cpan-outdated: príkaz nenájdený
cpan-outdated: příkaz nenalezen
cpan-outdated: команда не найдена
cpan-outdated: командата не е открита
cpan-outdated: 命令找不到
cpan-outdated: コマンドが見つかりません