push, pop, splice, shift, unshifting is a bit ugly, but works too.

my $data_source = {};

for( my $i = 0; $i < 10; $i++) {
   push @{$data_source->{a}}, "source a's data";
   push @{$data_source->{b}}, "source b's data";
   push @{$data_source->{c}}, "source c's data";
}
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