use POSIX qw(EINTR EWOULDBLOCK EAGAIN);
...
# Try to read 4096 bytes from $fh using sysread().  Icky.

my $data;
my $offset = 0;
my $length = 4096;

while($length > 0) # Handle partial reads
{
  my $read = sysread($fh, $data, $length, $offset);

  unless(defined $read)
  {
    next  if($! == EINTR || $! == EWOULDBLOCK || !$ == EAGAIN);
    # Handle other errors here
    ...
  }

  last  if($read == 0); # EOF

  $offset += $read;
  $length -= $read;
}