To solve the presented problem this type of approach is the one I would use too but with List::Util::uniq for speed and clarity. Core modules with XS are ideal for this type of task.

#!/usr/bin/env perl
use strict;
use warnings;
use List::Util 'uniq';

my $tags = '#tag1 #tag2 #tag3 #tag1';

my $uniq = join ' ', uniq split / /, $tags;

print "Orig: $tags\nUniq: $uniq\n";

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In reply to Re^2: Regex: remove non-adjacent duplicate hashtags by hippo
in thread Regex: remove non-adjacent duplicate hashtags by element22

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