perl.req.files: 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/perl.req.files - from package: perl-rpm-build-perl-scripts

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

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