runThePEG: 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/runThePEG - from package: thepeg

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

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