open-test-files.pl: 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/share/doc/librdf-query-perl/examples/bin/open-test-files.pl - from package: librdf-query-perl

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

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