( Please put code in <c>...</c> tags. )

( Please don't lie by saying your code outputs one thing when it doesn't even compile. Post the code you actually ran. )

The splitting occurs because "=====" is indeed not equal to "==.*". It's one character longer, for starters. Fix:

while (<>) {
    chomp;
    my @a;
    @a = split if !/^==/;
    print "@a\n";
}
[download]

But it makes no sense to process @a if you didn't put anything in it. Maybe you want

while (<>) {
    chomp;
    next if /^==/;
    my @a = split;
    print "@a\n";
}
[download]