mod2html.pl: 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/share/sympa/bin/mod2html.pl - from package: sympa

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

Error in other languages:
mod2html.pl: bevel nie gevind nie
mod2html.pl: comandă negăsită
mod2html.pl: comando não encontrado
mod2html.pl: commande introuvable
mod2html.pl: command not found
mod2html.pl: käsku ei ole
mod2html.pl: không tìm thấy lệnh
mod2html.pl: komanda nerasta
mod2html.pl: Kommando nicht gefunden.
mod2html.pl: kommandot finns inte
mod2html.pl: komut yok
mod2html.pl: nie znaleziono polecenia
mod2html.pl: níor aimsíodh an t-ordú
mod2html.pl: no se encontró la orden
mod2html.pl: no s'ha trobat l'ordre
mod2html.pl: opdracht niet gevonden
mod2html.pl: parancs nem található
mod2html.pl: perintah tidak ditemukan
mod2html.pl: príkaz nenájdený
mod2html.pl: příkaz nenalezen
mod2html.pl: команда не найдена
mod2html.pl: командата не е открита
mod2html.pl: 命令找不到
mod2html.pl: コマンドが見つかりません