Sending a transcript to a SMTP server nicely

play.pl

#!/usr/bin/env perl

use strict;
use warnings;
use feature ':5.10';
use autodie qw/open/;

my $file = shift;
open my $fh, '<', $file;

$| = 1;
my $seen_data = 0;

outer: while(<>){
    print {*STDERR} "< $_";

    my $line;
    inner: while(1){
        $line = <$fh>;
        next outer unless defined $line;
        chomp $line;
        print {*STDERR} "> $line\n";
        print "$line\r\n";
        last inner unless $seen_data;
    }
    $seen_data = $line eq 'DATA';
}

script

HELO snowball2.jrock.us
MAIL FROM: [email protected]
RCPT TO: [email protected]
DATA
Hello there.
.

transcript

[~] 0 (jon@snowball2)
$ socat system:'perl play.pl script' tcp-connect:itchy.internal:25
< 220 itchy.jrock.us ESMTP Exim 4.72 Tue, 27 Dec 2011 02:16:38 -0600
> HELO snowball2.jrock.us
< 250 itchy.jrock.us Hello snowball2.internal [10.0.0.5]
> MAIL FROM: [email protected]
< 250 OK
> RCPT TO: [email protected]
< 250 Accepted
> DATA
< 354 Enter message, ending with "." on a line by itself
> Hello there.
> .
< 451 Temporary local problem - please try later
^C