First of all, in reply to John M. Dlugosz, please don't use eq: use constant ROFLAG => $^O =~ /win32/i ? 0444 : 0644;

There is too much legacy code that does so already. If everyone used a regex $^O could be changed to contain more details about the exact version of Windows.

However, this solution strikes me as an ugly hack anyway. How about this?

chmod +(stat)[2] | 0444, $_ for $installfile;

Makeshifts last the longest.