Yes, that's possible, assuming your applet can load images via URLs.

my $q = CGI->new();

my $data = create_png_image_data();

binmode STDOUT;
print $q->header( -type => 'image/png' );
print $data;
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If you have a small set of possible images, I would suggest you create them once and save them as normal web-accessible png files, though. Then you won't need the perl code anymore, which will make your application a lot more efficient.