simplecal.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/doc/libintl-perl/examples/simplecal/bin/simplecal.pl - from package: libintl-perl

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

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