plsql-diff.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/dotlrn/bin/plsql-diff.pl - from package: dotlrn
/usr/share/openacs/bin/plsql-diff.pl - from package: openacs

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

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