ppod2docbook: 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/ppod2docbook - from package: perl-Pod-PseudoPod

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

Error in other languages:
ppod2docbook: bevel nie gevind nie
ppod2docbook: comandă negăsită
ppod2docbook: comando não encontrado
ppod2docbook: commande introuvable
ppod2docbook: command not found
ppod2docbook: käsku ei ole
ppod2docbook: không tìm thấy lệnh
ppod2docbook: komanda nerasta
ppod2docbook: Kommando nicht gefunden.
ppod2docbook: kommandot finns inte
ppod2docbook: komut yok
ppod2docbook: nie znaleziono polecenia
ppod2docbook: níor aimsíodh an t-ordú
ppod2docbook: no se encontró la orden
ppod2docbook: no s'ha trobat l'ordre
ppod2docbook: opdracht niet gevonden
ppod2docbook: parancs nem található
ppod2docbook: perintah tidak ditemukan
ppod2docbook: príkaz nenájdený
ppod2docbook: příkaz nenalezen
ppod2docbook: команда не найдена
ppod2docbook: командата не е открита
ppod2docbook: 命令找不到
ppod2docbook: コマンドが見つかりません