MIME::Lite is a fine (and more reliable) option, but seeing we are just shelling out to scp why not just invoke sendmail directly by opening a pipe and sending it the required data:

my $sendmail = "/usr/sbin/sendmail -t";

open MAIL, "|$sendmail" or die "Cannot open $sendmail: $!";
print MAIL <<EMAIL;
Reply-to: $reply_to
Subject: $subject
To: $send_to
Content-type: text/plain

$content
.

EMAIL
close MAIL;
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