In the "TK Gotchas" section of this tutorial page you will find the following comment:

if you create a Canvas with Photos in it, it appears to be impossible to destroy them without leaking memory, no matter how many lexical scopes you leave or destroys and deletes you scream at the interpreter. The only work around I found was to load the images in, and simply hide them when not required.

Hopefully a TK guru will post a more concise solution to this problem.

On a related note, Steve Cook has a wonderful set of introductory tutorials related to perl/tk. See his pages for details.

{
    my (@imagelist);
    foreach ( 0 .. $#filelist ) {
        print $filelist[$_], "\n";
        my $temp = $mw->Photo( -file => $filelist[$_] );
        push( @imagelist, $temp );
    }
    eval {
        my $thumb = $mw->Thumbnail(
            -images  => [@imagelist],
            -ilabels => 1
        )->pack;
    };
    warn($@) if ($@);
}
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With Photo objects, you need to create a set of them once, and REUSE them. You can reuse a photo object with

 $thumbs{0}->blank;
 $thumbs{0}->read($info{'admin'}{'thumbnail'});
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Also when you create the thumbs, just make 1 "big-photo object" and reuse it in a loop, to make the thumb-objects. Then push the smaller "thumb-objects" into the @imagelist, instead of the huge full-photo-objects.

Here is a sample bit of code which shows how to make thumbnails in a loop, with just a single imager object. Now, I'm actually creating the thumbnails in the thumbs dir, but you could just push them into a hash. However....you will still reach memory limits if you try to push too many thumbs into a hash. So you must carefully think about juggling and reusing everything, so as to keep your mem use as low as possible. There are many ways to do this, so you have to find the modules which you like working with, and figure out how to use them in unison, without wasting objects.

sub make_thumbs{

my @pics = <pics/*.jpg pics/*.gif pic/*.png>;
my $imager = Imager->new();

foreach my $pic (@pics){
   my ($basename,$path,$suffix) = fileparse($pic,@exts);
   $info{$basename}{'key'} = $basename;
   $info{$basename}{'name'} = $basename;
   $info{$basename}{'pic'} = "pics/$basename.jpg"; #convert to jpg
   $info{$basename}{'thumbnail'} = "thumbs/$basename.jpg";

$imager->open(file=>$pic) or die $imager->errstr();

# Create smaller version
my $thumb = $imager->scale(xpixels=>100);
print "Storing thumbnail as: thumbs/$basename.jpg\n";
$thumb->write(file=>"thumbs/$basename.jpg",
jpegquality=>30) or die $thumb->errstr;

#Create resized picture
my $resizer = $imager->scale(ypixels=>400);
print "Storing resize as: pics/$basename.jpg\n";
$resizer->write(file=>"pics/$basename.jpg",
jpegquality=>90) or die $resizer->errstr;

}

undef $imager;
print "\n#################endofthumbcreation##########################
+#####\n";

}
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It also has a command to identify the thumbnail which you could use to open the photo in another toplevel window when you click on a thumb.

#!/usr/bin/perl -w
use Tk;
use Tk::Thumbnail;
use strict;

#adapted from Mastering Perl/Tk 

my $mw = MainWindow->new;

my $tn = $mw->Thumbnail(
    -images     => [<*.jpg>],
    -command    => sub {
        my $i = $_[0]->cget(-image);
        print "args=@_, image=$i\n";
    },
    @ARGV);
$tn->pack;

MainLoop;
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