"on your site"...

Who's code was it?

Code corrections:

#!/usr/bin/perl -w
use strict;
my $o;
sub unique {
  my $self=shift;
  my %tmp;
  
  map { $tmp{$_}=1 } @_;
  return keys %tmp;
}

my @array = qw(apples cheeries apples bananas apples);
#$o->unique(@array);
print unique(@array);

1;
[download]

$o->unique means you are calling the unique method of the $o object, which your code doesn't show being instantiated anywhere. The problem you listed was with the %tmp, which is basically incorrect syntax when you are trying to assign a value to a hash element.