regmerge: 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 CentOS possible default full paths are:

/usr/lib64/libreoffice/ure/bin/regmerge - from package: libreoffice-ure

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/lib/debug/usr/lib/ure/bin/regmerge - from package: ure-dbg
/usr/lib/ure/bin/regmerge - from package: ure

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

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