"\n" =~ /\n.*\z/;   # matches
[download]

Obvious, I think.

If this one is obvious, then the original one should be obvious too. Compare:

"\n" =~ /\n.*\z/;   # matches
"\n" =~   /.*\z/;   # should match but doesn't
[download]

The pattern gets shorter, but doesn't match any more...