You may need to adjust the parameters you pass to new(). E.g. with

perl -MFile::Tail -E '$f = File::Tail->new(q[/var/log/foo/bar.log]); p
+rint $l while $l = $f->read'
[download]

I had to wait 9 seconds before output was produced. But with

perl -MFile::Tail -E '$f = File::Tail->new(name=> q[/var/log/foo/bar.l
+og], tail=>10, maxinterval=>0.5); print $l while $l = $f->read'
[download]

The output appears right away.