pbyacc: 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/pbyacc - from package: perl-byacc

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

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