Looks like a HTTP 500 error is being returned by web server. Not sure why, but I'm sure it doesn't help that you send a newline as part of the date. chomp!

my @date;

open(IN, "<c:/perl/scripts/dates/dates.txt");
while (<IN>) {
    push (@date, $_);
    }
close(IN);
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should be

open(my $in, '<', "c:/perl/scripts/dates/dates.txt")
    or die "open: $!\n";

my @date;
while (<$in>) {
    chomp;
    push(@date, $_);
}
close($in);
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which can be written as

open(my $in, '<', "c:/perl/scripts/dates/dates.txt")
    or die "open: $!\n";

chomp( my @date = <$in> );

close($in);
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