<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _process_dependencies(self, anexec, contents, mode="insert"):
 """Extracts a list of subroutines and functions that are called from within this executable. :arg mode: specifies whether the matches should be added, removed or merged into the specified executable. """

        #At this point we don't necessarily know which module the executables are
        #in, so we just extract the names. Once all the modules in the library
        #have been parsed, we can do the associations at that level for linking.
        for dmatch in self.RE_DEPEND.finditer(contents):
            isSubroutine = dmatch.group("sub") is not None
            if "!" in dmatch.group("exec"):
                execline = self._depend_exec_clean(dmatch.group("exec"))
            else:
                execline = "(" + dmatch.group("exec").split("!")[0].replace(",", ", ") + ")"

            if not "::" in execline:
                try:
                    dependent = self.nester.parseString(execline).asList()[0]
                except:
                    msg.err("parsing executable dependency call {}".format(anexec.name))
                    msg.gen("\t" + execline)
            
                #Sometimes the parameter passed to a subroutine or function is 
                #itself a function call. These are always the first elements in
                #their nested lists.
                self._process_dependlist(dependent, anexec, isSubroutine, mode)