falcon: 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/falcon - from package: falconpl

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

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