regress: 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/lib/cmtk/bin/regress - from package: cmtk

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

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