scanimage-perl: 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/scanimage-perl - from package: gscan2pdf

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

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