I wrote about this topic at length here. In this case, assuming this is on Windows, you might want to just use Win32::ShellQuote, e.g. its quote_system_list - but make sure to read the module's documentation in any case.

Update: For example, system(quote_system_list('NET','USE','g:','\\\\<NETWORK DRIVE>\\<NETWORK FOLDER>',$pw,'/user:<USERNAME>'))==0 or die "system failed, \$?=$?";