varnish_reload_vcl: command not found

Have You tried accessing the binary with the full path?

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH

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/sbin/varnish_reload_vcl - from package: varnish

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