I see lots of code, but I don't see any Button code. This might be helpful: I know what I mean. Why don't you?.

This bit of code looks ominous. Use of a recursive function call is not appropriate for doing retries. Among other things it can chew up a lot of stack space. You don't show what initialize_all_variables() does, but I see no other retry loop going on.

if ( $project_dir_exists_error eq "Retry" ) {
                &initialize_all_variables;
            }
[download]

If the button is "not quickly response" to your letting go of the mouse button, you may have some code that is chewing an incredible amount of CPU time. Again simplify the code down to an example similar in size to the one that I posted.

Oh this ampersand in front of a subroutine name is an older style. Nowadays, initialize_all_variables(); would be considered better.