voms-ac-issue.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 CentOS possible default full paths are:

/usr/bin/voms-ac-issue.pl - from package: perl-VOMS-Lite

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

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