tclsh8.6: 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/tclsh8.6 - from package: tcl8.6

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

Error in other languages:
tclsh8.6: bevel nie gevind nie
tclsh8.6: comandă negăsită
tclsh8.6: comando não encontrado
tclsh8.6: commande introuvable
tclsh8.6: command not found
tclsh8.6: käsku ei ole
tclsh8.6: không tìm thấy lệnh
tclsh8.6: komanda nerasta
tclsh8.6: Kommando nicht gefunden.
tclsh8.6: kommandot finns inte
tclsh8.6: komut yok
tclsh8.6: nie znaleziono polecenia
tclsh8.6: níor aimsíodh an t-ordú
tclsh8.6: no se encontró la orden
tclsh8.6: no s'ha trobat l'ordre
tclsh8.6: opdracht niet gevonden
tclsh8.6: parancs nem található
tclsh8.6: perintah tidak ditemukan
tclsh8.6: príkaz nenájdený
tclsh8.6: příkaz nenalezen
tclsh8.6: команда не найдена
tclsh8.6: командата не е открита
tclsh8.6: 命令找不到
tclsh8.6: コマンドが見つかりません