At times getline will block when there is no new data

I'll repeat: No, it won't.

$ perl -le'$|=1; for (;;) { print "poke"; sleep 1; }' > file & perl -M
+IO::Handle -e'sleep 3; print while $_ = STDIN->getline; print "exited
+ instead of blocking\n"' < file ; fg
[1] 29483
poke
poke
poke
poke
exited instead of blocking
perl -le'$|=1; for (;;) { print "poke"; sleep 1; }' > file
^C

$ cat file ; rm file
poke
poke
poke
poke
poke
poke
[download]