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 CentOS possible default full paths are:

/var/spool/hylafax/bin/dict/pl - from package: hylafax+
/usr/bin/pl - from package: pl

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

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