lablgtk2: 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/lablgtk2 - from package: ocaml-lablgtk

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

On Debian possible default full paths are:

/usr/bin/lablgtk2 - from package: liblablgtk2-ocaml-dev

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

Error in other languages:
lablgtk2: bevel nie gevind nie
lablgtk2: comandă negăsită
lablgtk2: comando não encontrado
lablgtk2: commande introuvable
lablgtk2: command not found
lablgtk2: käsku ei ole
lablgtk2: không tìm thấy lệnh
lablgtk2: komanda nerasta
lablgtk2: Kommando nicht gefunden.
lablgtk2: kommandot finns inte
lablgtk2: komut yok
lablgtk2: nie znaleziono polecenia
lablgtk2: níor aimsíodh an t-ordú
lablgtk2: no se encontró la orden
lablgtk2: no s'ha trobat l'ordre
lablgtk2: opdracht niet gevonden
lablgtk2: parancs nem található
lablgtk2: perintah tidak ditemukan
lablgtk2: príkaz nenájdený
lablgtk2: příkaz nenalezen
lablgtk2: команда не найдена
lablgtk2: командата не е открита
lablgtk2: 命令找不到
lablgtk2: コマンドが見つかりません