According to the docs, "PerlApp first determines which modules and external files the converted script depends upon. The PerlApp program starts this process by scanning the script source code". Problem is that promise does not include whatever source code the dependent modules are themselves dependent on. So my best guess is you have to put in a use or require specifically for each indirect dependency.
Update: Just seen an intervening post with --add, hmm having googled for it I found only one minus i.e. -add. oh well, might be preferable to use such an option)