Your substitution looks for <-- (you might have wanted <!--) and then matches a single character that's not > or <, followed by -->. Probably not what you want.

A simple approach (although by no means 100% reliable) would be

    $question =~ s/<!--.*?-->//sg;
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To reliably remove comments from HTML, use HTML::Parser or a related module.

Or, even fancier, use File::Comments:

#!/usr/bin/perl -w
use strict;
use File::Comments;

my $stripper = File::Comments->new();
my $stripped = $stripper->stripped("foo.html");
print "$stripped\n";
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