# %columns will become the hash of arrays
my %columns;

# Foreach row of data collect its keys and create an empty array in %columns
$columns{$_} //= [] foreach map { keys %$_ } @$data;

# Then, for each row
foreach my $row ( @$data ) {
  # push the value foreach column
  push @{$columns{$_}}, $row->{$_} foreach keys %columns;
}