lwp-mirror: 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 CentOS possible default full paths are:

/usr/bin/lwp-mirror - from package: perl-libwww-perl

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/lwp-mirror - from package: libwww-perl

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

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