dns_conf.pl: 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/gforge/bin/dns_conf.pl - from package: gforge-dns-bind9

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

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