tabmerge: 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/bin/tabmerge - from package: perl-Text-RecordParser

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

On Debian possible default full paths are:

/usr/bin/tabmerge - from package: libtext-recordparser-perl

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

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