" I think you need to change the extension of ur image file to either JPG for processing the file "
Why do you think that? Isn't a file just a file, even on Windows? All the extension does is allow windows to know what viewer/editor/or program to associate and/or launch when you double click that file? I don't see how the extension could affect reading the file...

"empty the arrays or hash or the any data structure whichever you are using after using it rather than over witing it."
Is this what you mean by that?

my @images = qw(file1.png file2.png file3.png);
@images = ();
@images = qw(file4.png file5.png file6.png);
[download]

If so, why is that better than this?

my @images = qw(file1.png file2.png file3.png);
@images = qw(file4.png file5.png file6.png);
[download]

Update:
Perhaps you meant that you need to empty your data structure periodically if you are pushing or unshifting onto it, as it would continue to grow otherwise?