What you want is to eliminate duplicate elements from a list. Here's one solution, from the Perl cookbook (via RE: Return a Unique Array):

my %seen =() ;
@unique_array = grep { ! $seen{$_}++ } @non_unique_array ;
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Put that into a sub:

sub dedup {
  my %seen;
  grep { ! $seen{$_}++ } @_;
}
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and you can simply do

@tapes = qw(tape1 tape2 tape1 tape3 tape2 tape1);
print join(' ',dedup(@tapes)),"\n";
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to join tapes together with no duplicates.