Mail::Internet is a useful module for parsing email messages.

If you don't want the overhead of using modules, you could do something like:

my $from;
while (<MAIL>) {
    my $mail = $_;
    chomp $mail;
    next unless substr($mail, 0, 6, '') eq 'From: ';
    $from = $mail;
    last;
}
print "Mail from : $from\n";
[download]