Re^2: How do I test if a bit has been set in a bitstring

[AnomalousMonk]

my ($flags)    = $filename  =~ / \. ([0-9a-fA-F]+) $ /x;

[0-9a-fA-F] is also available (and, IMHO, preferable) as the  [[:xdigit:]] POSIX character class. See POSIX Character Classes in perlre for info on this and its many Unicode  \p{Property} cousins.