import: cpan: Move core-module? to top-level.

* guix/import/cpan.scm (cpan-module->sexp): Move local core-module?
procedure to ...
(core-module?): ... here.

guix/import/cpan.scm

@@ -116,23 +116,7 @@ if the original's domain was metacpan."
       (and (access? core X_OK)
            core))))
 
-(define (cpan-module->sexp meta)
+(define core-module?
-  "Return the `package' s-expression for a CPAN module from the metadata in
-META."
-  (define name
-    (assoc-ref meta "distribution"))
-
-  (define (guix-name name)
-    (if (string-prefix? "perl-" name)
-        (string-downcase name)
-        (string-append "perl-" (string-downcase name))))
-
-  (define version
-    (match (assoc-ref meta "version")
-      ((? number? vrs) (number->string vrs))
-      ((? string? vrs) vrs)))
-
-  (define core-module?
   (let ((perl-version (package-version perl))
         (rx (make-regexp
              (string-append "released with perl v?([0-9\\.]*)"
@@ -157,6 +141,22 @@ META."
                                        first perl-version last))))
                            (loop)))))))))))
 
+(define (cpan-module->sexp meta)
+  "Return the `package' s-expression for a CPAN module from the metadata in
+META."
+  (define name
+    (assoc-ref meta "distribution"))
+
+  (define (guix-name name)
+    (if (string-prefix? "perl-" name)
+        (string-downcase name)
+        (string-append "perl-" (string-downcase name))))
+
+  (define version
+    (match (assoc-ref meta "version")
+      ((? number? vrs) (number->string vrs))
+      ((? string? vrs) vrs)))
+
   (define (convert-inputs phases)
     ;; Convert phase dependencies into a list of name/variable pairs.
     (match (flatten