Why does Perl affect the output of my print?

It's been a couple of months since I was Perling, but I'm completely fixated on why this is happening ...

I'm on OSX if that matters.

I am trying to convert strings to a file like

03/08/2011 01:00 PDT, 1.11

to stdout lines like

XXX, 20120803, 0100, KWH, 0.2809, A, YYY

Since I am reading a file, I want chompafter reading each line. However, when I chomp, I find that my seal is all messed up. When I'm not chomp, printing is fine (except for the extra line of a new line ...). What's going on here?

while(<SOURCE>) {
    chomp;
    my @tokens = split(' |,');     # @tokens now [08/03/2011, 01:00, PDT, 1.11]

    my $converted_date = convertDate($tokens[0]);
    my $converted_time = convertTime($tokens[1]);

print<<EOF;
$XXX, $converted_date, $converted_time, KWH, $tokens[3], A, YYY
EOF
}

With an incoming call, the chompoutput is all mixed up:

, A, YYY10803, 0100, KWH, 1.11

Without calling chompthere, it at least prints in the correct order, but with an additional new line:

XXX, 20110803, 0100, KWH, 1.11
, A, YYY

, chomp "" . autoflush $|=1;, , .

? ....