Generally speaking,

• Arrays are good when you want to maintain ordering.
• Hashes are good when you need to handle uniqueness constraints, or when you want to make multiple lookups of data based on some value.

# Remove duplicates from an array using a hash.

# create starting array.
@dupes = qw( a a b b b b a c b a c c b );

# use hash slice to create hash entries.
@unique{@dupes} = ();
# pretty much like:
# foreach( @dupes ) {
#     $unique{$_} = undef;
# }

@unique = keys %unique;


print "@unique\n";
#prints
#  c a b
# if you want keys in order you can use
# @unique = sort keys %unique;
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