purple-client-example: 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/purple-client-example - from package: libpurple

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

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