viewperl: 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/bin/viewperl - from package: libsyntax-highlight-perl-improved-perl

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

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