some problem in syntax.pl

Hi, I am Hyojung Hwang and working for Korea Telecom. 
I am using ripe dbase software. 
I found some problem or starnge things in this code. 
In syntax.pl, checking 'auth' attribute, 
---
        elsif ($authstr[0] eq "MAIL-FROM") {
            local($regex) = $value;
            $regex =~ s/^\s*MAIL\-FROM\s*//;
            eval "/$regex/;";
            if ($@) {
                return $O_ERROR, "\"$regex\" is not a legal regular expression";
            }
            else {
                return $O_OK;
            }
        }
--- 

  why do you eval check ? 
  Isn't this necessary ? 
  Rather, I think, $regex is checked if it is valid email address.
  How do you think about it ? 
  If it is necessary, please explain why this is needed . 
  Thanks in advance !!

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    *    _  _	  ==GD@: 56 at L0m Hq8A@: 1$1b at L4Y.
    ||_|| ||_| 	  Hwang, Hyojung / jung at jean.kotel.co.kr / 82-2-526-5235
  |_|       _|_	  Internet Team  / Multimedia Laboratory / KT R&D Group
           |_|	  137-792, 17 Umyun-Dong, Seocho-Gu, Seoul, Korea