! thank you, Blei. I'm not sure why it wasn't working before
! when I tried it while talking to you, but now it works fine.
! here is what I'm using now. I had tried this same thing
! when you showed me your code (adapting \ void to void
! and pointer: void to void*) but I was still crashing my
! instance of Factor. must've been code gremlins.
! Either way, thanks, and here goes what I have now.

CALLBACK: void* pcre_malloc_t ( size_t size ) ;
C-GLOBAL: pcre_malloc_t pcre_malloc
: pcre-malloc ( size -- ptr )
    pcre_malloc void* { size_t } cdecl alien-indirect ;

CALLBACK: void pcre_free_t ( void* ptr ) ;
C-GLOBAL: pcre_free_t pcre_free
: pcre-free ( ptr -- )
    pcre_free void { void* } cdecl alien-indirect ;
DESTRUCTOR: pcre-free

! now this works:
[ "some pattern" new-regex &pcre-free ] with-destructors
! returns a now-invalid (just-freed) pointer, which is correct.