couriergraph.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/sbin/couriergraph.pl - from package: couriergraph

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

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