Another way to do it:

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

my @data = (
    '$?/1dlw&', '*%1sdh^?', '@/!1dlw\\/',
    '$£1cgi*&', '?@1sdh%&', '~#1xnf$%'
);

my @patterns = qw/1dlw 1sdh 1cgi 1xnf/;
my $re = join "|", map quotemeta, @patterns;

my %seen;
for (@data) {
    next unless /($re)/;     # shouldn't happen, presumably
    if (defined $seen{$1}) {
        push @{ $seen{$1} }, $_;
    } else {
        $seen{$1} = [ $_ ];
    }
}

my @unique = map {
    @{ $seen{$_} } == 1 ? $seen{$_}->[0] : ()
} keys %seen;
[download]

Edit: Or another way...

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

my @data = (
    '$?/1dlw&', '*%1sdh^?', '@/!1dlw\\/',
    '$£1cgi*&', '?@1sdh%&', '~#1xnf$%'
);

my @patterns = qw/1dlw 1sdh 1cgi 1xnf/;
my $re = join "|", map quotemeta, @patterns;

my %seen;
/($re)/ and $seen{$1}++ for (@data);

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

— Arien