What I am trying to do is: ...

O.K., but what do you want to do with $main_template if there are no results? Leave %%searchresults%% there? Or do you want to erase it? I assume you want to erase it.

Here's enough of a start that you should be able to figure the rest out yourself:

  # join results into a single variable; this may be empty
  my $results = join('', @results);
  # do the substitution.
  $main_template =~ s/%%searchresults%%/$results/g;
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