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#!/usr/bin/perl
use strict;
use warnings;
...
my @unique = map {
    @{ $seen{$_} } == 1 ? $seen{$_}->[0] : ()
} keys %seen;

#!/usr/bin/perl
use strict;
use warnings;
...

my $unique = join "|", map quotemeta, grep { $seen{$_} == 1 } @pattern
+s;
my @unique = grep { /$unique/ } @data;