You can binary AND them with the constants provided by the module to test for a single flag. The following will give you a comma-separated list of flags for a single packet.

my %tcp_flags=(FIN => FIN,
               SYN => SYN,
               RST => RST,
               PSH => PSH,
               ACK => ACK,
               URG => URG,
               ECE => ECE,
               CWR => CWR);

my $cur_flags=$tcp_obj->{flags};
my @set_flags =
  grep { $cur_flags & $tcp_flags{$_} }
    keys %tcp_flags;

print join(",",@set_flags)."\n";
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