perl -MFile::Find -e 'find(sub {my $f = $File::Find::name; print $f, "\n" if -w $f && !-l $f}, "/")'

##</code><code>##

use File::Find::Rule::Permissions;
my $user = @ARGV ? $ARGV[0] : $ENV{USER};
print $_,"\n" for File::Find::Rule::Permissions->file()
 ->permissions( user => $user, isWriteable => 1)
 ->in("/");