squid-purge: 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
/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 Debian possible default full paths are:

/usr/lib/debug/usr/bin/squid-purge - from package: squid3-dbg
/usr/bin/squid-purge - from package: squid-purge

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