use warnings;
use strict;
use Data::Dump qw(pp);

my $data = [
  {a => 1, b => 2},
  {a => 3, b => 4},
  {a => 5, b => 6},
];

# create data struct like this
#
# my $required = {  a => [1, 3, 5],  b => [2, 4, 6],};

my %required;
foreach my $href (@$data)
{
   push @{$required{$_}}, $href->{$_} foreach keys %$href;
}

pp \%required; #{ a => [1, 3, 5], b => [2, 4, 6] }