foreach (qw/hasha hashb hashc/) {
  @keys = keys eval('%' . $_);
  print "There are " . scalar(@keys) . " keys here for '$_'\n";
}

##</code><code>##

my %big_data = (
  hasha => \%hasha,
  hashb => \%hashb,
  hashc => \%hashc,
);

foreach (qw/hasha hashb hashc/) {
  @keys = keys %{$big_data{$_}};
  print "There are " . scalar(@keys) . " keys here for '$_'\n";
}