swipl: 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/swipl - from package: swi-prolog-nox
/usr/lib/swi-prolog/bin/amd64/swipl - from package: swi-prolog-nox

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

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