mewl: 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/mewl - from package: mew-beta-bin
/usr/bin/mewl - from package: mew-bin

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

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