prepare-vhosts-file.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/prepare-vhosts-file.pl - from package: gforge-web-apache2-vhosts

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

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