libdecodeqr-webcam: 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/libdecodeqr-webcam - from package: libdecodeqr-examples

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

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