pbespp: 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/pbespp - from package: mcrl2

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

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