$ strace perl -e'$/ = \512; 1 while <STDIN>' <a 2>&1 | grep 'read(0'
read(0, "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"..., 8192) = 8192
read(0, "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"..., 8192) = 8192
read(0, "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"..., 8192) = 3616
read(0, "", 8192)                       = 0