xpl2gpl: 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/bin/xpl2gpl - from package: tcptrace

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

Error in other languages:
xpl2gpl: bevel nie gevind nie
xpl2gpl: comandă negăsită
xpl2gpl: comando não encontrado
xpl2gpl: commande introuvable
xpl2gpl: command not found
xpl2gpl: käsku ei ole
xpl2gpl: không tìm thấy lệnh
xpl2gpl: komanda nerasta
xpl2gpl: Kommando nicht gefunden.
xpl2gpl: kommandot finns inte
xpl2gpl: komut yok
xpl2gpl: nie znaleziono polecenia
xpl2gpl: níor aimsíodh an t-ordú
xpl2gpl: no se encontró la orden
xpl2gpl: no s'ha trobat l'ordre
xpl2gpl: opdracht niet gevonden
xpl2gpl: parancs nem található
xpl2gpl: perintah tidak ditemukan
xpl2gpl: príkaz nenájdený
xpl2gpl: příkaz nenalezen
xpl2gpl: команда не найдена
xpl2gpl: командата не е открита
xpl2gpl: 命令找不到
xpl2gpl: コマンドが見つかりません