ciderwebmail_fastcgi.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/ciderwebmail/bin/ciderwebmail_fastcgi.pl - from package: ciderwebmail

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

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