rpmorphan.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 CentOS possible default full paths are:

/usr/bin/rpmorphan.pl - from package: rpmorphan

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

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