stateless_proxy.pl.gz: 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/share/doc/libnet-sip-perl/examples/bin/stateless_proxy.pl.gz - from package: libnet-sip-perl

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

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