Perhaps, this will be of some help.
(Probably not.)
C-Script file copy;
tested
Use \\ as path separator and workdir (ifdef DEVELOP) and exedir (ifelse) respectively.
Code:
/************************************
	filef_copy
*************************************/
var file_nFrom = 0;
var file_nTo = 0;
var file_nByte;

function filef_copy(_sFrom, _sTo) {
	var ret1; ret1 = 0;
	file_nByte = 0;
	file_nFrom = 0;
	file_nTo = 0;
	if (_sFrom == 0) {
		return(0); 
	}
	if (_sTo == 0) {
		return(0);
	}

	file_nFrom = file_open_read(_sFrom);
	if (file_nFrom == 0) {
		error("!error filef_copy: file from not found!");
		return(0);
	}
	
	file_nTo = file_open_write(_sTo);
	if (file_nTo == 0) {
		error("!error filef_copy: file to not found!");
		return(0);
	}
	while(1) {
		file_nByte = file_asc_read(file_nFrom);
		if (file_nByte != -1) { 
			file_asc_write(file_nTo, file_nByte);
			ret1 += 1; 
		} else {
			break;
		}
	}
	file_close(file_nFrom);
	file_close(file_nTo);
	return(ret1);
}