Without commenting on the rest of the code, I thought I'd point out that this:

    if($in{'go'} eq 'perldoc'){
use Pod::Html;
    }
    if($in{'file'} =~ /edit/ or /save/){
use HTML::Entities;
    }
    if( ($in{'rd'}) 
    or ( ($in{'file'} eq 'save') && ($in{'filename'}) ) 
    or ($in{'go'} eq ' url ')){
use FindBin qw($Bin);
use File::Spec::Functions qw(rel2abs);
    }
    if($diag eq '1'){
use Data::Dumper;
    }
[download]

isn't doing what you think it's doing.

'use' happens at compile time, not run-time, so this fragment is actually just a wasteful way of doing:

use Pod::Html;
use HTML::Entities;
use FindBin qw($Bin);
use File::Spec::Functions qw(rel2abs);
use Data::Dumper;

if($in{'go'} eq 'perldoc'){
  # do nothing
}

if($in{'file'} =~ /edit/ or /save/){
  # do nothing
}

if( ($in{'rd'}) 
    or ( ($in{'file'} eq 'save') && ($in{'filename'}) ) 
    or ($in{'go'} eq ' url ')){
  # do nothing
}

if($diag eq '1'){
  # do nothing
}
[download]

HTH.

Tony