dfg2otter.pl: 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/dfg2otter.pl - from package: spass

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

Error in other languages:
dfg2otter.pl: bevel nie gevind nie
dfg2otter.pl: comandă negăsită
dfg2otter.pl: comando não encontrado
dfg2otter.pl: commande introuvable
dfg2otter.pl: command not found
dfg2otter.pl: käsku ei ole
dfg2otter.pl: không tìm thấy lệnh
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dfg2otter.pl: Kommando nicht gefunden.
dfg2otter.pl: kommandot finns inte
dfg2otter.pl: komut yok
dfg2otter.pl: nie znaleziono polecenia
dfg2otter.pl: níor aimsíodh an t-ordú
dfg2otter.pl: no se encontró la orden
dfg2otter.pl: no s'ha trobat l'ordre
dfg2otter.pl: opdracht niet gevonden
dfg2otter.pl: parancs nem található
dfg2otter.pl: perintah tidak ditemukan
dfg2otter.pl: príkaz nenájdený
dfg2otter.pl: příkaz nenalezen
dfg2otter.pl: команда не найдена
dfg2otter.pl: командата не е открита
dfg2otter.pl: 命令找不到
dfg2otter.pl: コマンドが見つかりません