# pretty much the same as above (weak, i know)
while (<>) {
  my %h;
  push @entries, do { my %h; @h{@fieldnames} = split /,/; \%h };
}

# different, but still using a temp var
while (<>) {
  my @f = @fieldnames;
  push @entries, { map { shift @f => $_ } split /,/ };
} 

# hmm. gets rid of the temp var, but it's pretty ugly.
while (<>) {
  push @entries, { map { push @fieldnames, shift @fieldnames;
                         $fieldnames[-1] => $_ } split /,/ };

}

# tye++ (see http://www.perlmonks.org/index.pl?node_id=44763)
use mapcar;
while (<>) {
  push @entries, { mapcar { @_ } \@fieldnames, [ split /,/ ] };
}