tk5: 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 Debian possible default full paths are:

/usr/bin/tk5 - from package: tk5

You may install the required package with command apt-get install {package}

Error in other languages:
tk5: bevel nie gevind nie
tk5: comandă negăsită
tk5: comando não encontrado
tk5: commande introuvable
tk5: command not found
tk5: käsku ei ole
tk5: không tìm thấy lệnh
tk5: komanda nerasta
tk5: Kommando nicht gefunden.
tk5: kommandot finns inte
tk5: komut yok
tk5: nie znaleziono polecenia
tk5: níor aimsíodh an t-ordú
tk5: no se encontró la orden
tk5: no s'ha trobat l'ordre
tk5: opdracht niet gevonden
tk5: parancs nem található
tk5: perintah tidak ditemukan
tk5: príkaz nenájdený
tk5: příkaz nenalezen
tk5: команда не найдена
tk5: командата не е открита
tk5: 命令找不到
tk5: コマンドが見つかりません