Three random comments:

# Grab the current directory from $0. 
BEGIN
 {
  $0 =~ '(.*[\\\/])\w+\.\w+$';
  $curr_dir = $1 || "./";
 }
[download]

Probably better approach than using FindBin, but then use File::Basename to get the actual dirname().

my $display = &filter($q->param('display')) || '';
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Don't use the &-form of sub call: it is obsolete and likely not to do what you mean.

sub filter
{

if($_[0]){

  $_[0]=~s/\s+$//;
  $_[0]=~s/\'/\\\'/g;
  $_[0]=~s/<//g;
[download]

While better ways to do the same altogether have been suggested to you, when you have to do so, avoid such long chains of =~'s:

sub filter {
    my $str=shift;
    for ($str) {
        return '' unless $_;
        s/\s+$//;
        s/'/\\'/g;
        tr{<>;()\"\'?}{}d;
        s/<script//g;
    }
    $str;
}
[download]