purple-send: 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-send - from package: libpurple

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

On Debian possible default full paths are:

/usr/bin/purple-send - from package: libpurple-bin

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

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