xx-cond-replace: 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/xx-cond-replace - from package: xxdiff-scripts

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

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