Use meaningful variable names ($this is traditional for instance ... the docs can't guess what varname you're using)

Don't use global variables, you already have $frame , the globalest of the global things of your GUI application and all you could need or want, use it for storage

Invoke methods like methods not functions

Like this

$frame->DragAcceptFiles(1);
EVT_DROP_FILES( $frame, \&ondrop );
EVT_BUTTON( $frame, $ButExtract, \&onExtract );
## its like
## EVT_BUTTON( $parent, $child, \&callback );
## EVT_BUTTON( $parent, $child->GetId, \&callback );
...
sub ondrop {
    my( $frame, $wxDropFilesEvent ) = @_;
    my @files = $wxDropFilesEvent->GetFiles;
    $frame->{you_chose_these_files} = \@files;
    ## extract( $files[0] ); ## or whatever
}

sub onExtract {
    my( $frame, $extractBut ) = @_;
    my( $firstFile ) = @{    $frame->{you_chose_these_files}   };
    extract( $firstFile );
    ...
}
[download]

But dont get to comfortable because i will probably have more questions lol

I'm standing right now, but my laptop isn't high enough, so neck/back a little more stiff than usual ... still better than unadjustable hard dining room chair ... I'm done buying furniture :)