I think you are looking for a hash of arrays

  DB<126> $array
 => [
  { name => "Discount", reference => "100       ", type => "Paper" },
  { name => "Documents", reference => "100       ", type => "Paper" },
  { name => "Money", reference => "340       ", type => "Plastic" },
  { name => "State", reference => "40        ", type => "Cotton" },
  { name => "Slice", reference => "30        ", type => "Cotton" },
  { name => "Part", reference => "45        ", type => "Cotton" },
]
  DB<127> push @{ $hash{$_->{type}} }, $_->{name}  for @$array;

  DB<128> \%hash
 => {
  Cotton  => ["State", "Slice", "Part"],
  Paper   => ["Discount", "Documents"],
  Plastic => ["Money"],
}
[download]

update

  DB<136> use YAML

  DB<137> print Dump \%hash
---
Cotton:
  - State
  - Slice
  - Part
Paper:
  - Discount
  - Documents
Plastic:
  - Money
[download]

PS: Starting with Perl 5.14, push can take a scalar EXPR, which must hold a reference to an unblessed array. ... i.a.W. you won't need the @{...} part.