tmx2tmx: 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/bin/tmx2tmx - from package: libxml-tmx-perl

You may install the required package with command apt-get install {package}
Error in other languages:
tmx2tmx: bevel nie gevind nie
tmx2tmx: comandă negăsită
tmx2tmx: comando não encontrado
tmx2tmx: commande introuvable
tmx2tmx: command not found
tmx2tmx: käsku ei ole
tmx2tmx: không tìm thấy lệnh
tmx2tmx: komanda nerasta
tmx2tmx: Kommando nicht gefunden.
tmx2tmx: kommandot finns inte
tmx2tmx: komut yok
tmx2tmx: nie znaleziono polecenia
tmx2tmx: níor aimsíodh an t-ordú
tmx2tmx: no se encontró la orden
tmx2tmx: no s'ha trobat l'ordre
tmx2tmx: opdracht niet gevonden
tmx2tmx: parancs nem található
tmx2tmx: perintah tidak ditemukan
tmx2tmx: príkaz nenájdený
tmx2tmx: příkaz nenalezen
tmx2tmx: команда не найдена
tmx2tmx: командата не е открита
tmx2tmx: 命令找不到
tmx2tmx: コマンドが見つかりません