cwirc_frontend: 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/cwirc_frontend - from package: cwirc

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

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