pars: 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/lib/phylip/bin/pars - from package: phylip

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

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