polygon-mode: 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/lib64/piglit/bin/polygon-mode - from package: piglit

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

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