While I agree with the people above, using Mime::Something will save you in the long run, here is another answer to your question.
The main problem with your code above is that you are shoving the message into an array first. What you really want to do is break out of the first while
loop when you hit the blank line (denoting the end of the header).
last if /^$/; #Header is done!
print "From: $1\n\n" if /^From:(.+)$/; #Print the from address
while (<DATA>) #This while loop starts from where the other left off
Do you like green ecgs and ham?
Would you eat them in a house?
Would you eat them with a mouse?