qperf: 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/qperf - from package: qperf

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

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