在Perl中使用'unique'时如何从数组中查找'non-unique'值

Question

my @words = qw(1 2 3 4 4);
my @unique_words = uniq @words;

print @unique_words; # 1 2 3 4

I am interested in finding which value was non-unique, in this case 4 . And being able to set it equal to a variable so that I can keep track of which specific value was re-occuring.

I want to do this so I can implement a code that says "if my string contains duplicating value from array completely remove duplicating value from array from string". In this case, if a string contained 1 2 3 4 4 . I would like it after the if statement to contain 1 2 3 .

Answer 1

Counting/finding duplicates is easiest done with a hash:

my %count;
$count{ $_ }++ for @words;
print "$_ occurs more than once\n"
    for grep { $count{ $_ } > 1 } @words;

Finding the values that only occur once is done by looking for the elements in %count that have a count of 1:

my %count;
$count{ $_ }++ for @words;
my @unique_words = grep { $count{ $_ } == 1 } @words;