test_html.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/libtest-harness-perl/examples/bin/test_html.pl - from package: libtest-harness-perl

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

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