pl2wam: 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 CentOS possible default full paths are:

/usr/bin/pl2wam - from package: gprolog
/usr/lib64/gprolog-1.3.1/bin/pl2wam - from package: gprolog

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/lib/gprolog-iso/bin/pl2wam - from package: gprolog

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

Error in other languages:
pl2wam: bevel nie gevind nie
pl2wam: comandă negăsită
pl2wam: comando não encontrado
pl2wam: commande introuvable
pl2wam: command not found
pl2wam: käsku ei ole
pl2wam: không tìm thấy lệnh
pl2wam: komanda nerasta
pl2wam: Kommando nicht gefunden.
pl2wam: kommandot finns inte
pl2wam: komut yok
pl2wam: nie znaleziono polecenia
pl2wam: níor aimsíodh an t-ordú
pl2wam: no se encontró la orden
pl2wam: no s'ha trobat l'ordre
pl2wam: opdracht niet gevonden
pl2wam: parancs nem található
pl2wam: perintah tidak ditemukan
pl2wam: príkaz nenájdený
pl2wam: příkaz nenalezen
pl2wam: команда не найдена
pl2wam: командата не е открита
pl2wam: 命令找不到
pl2wam: コマンドが見つかりません