Try using the opendir function and CGI.pm for the drop-down menu, as such:

use CGI qw(:standard :html3);
opendir THISDIR, "docs/images" or die "failed opening: $!";
 @allfiles = grep !/^\.\.?$/, readdir THISDIR;
closedir THISDIR;
print popup_menu(-name=>'images',
                 -values=>\@allfiles);
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