Extract the flag, convert it to hex, then bitwise-AND it with the flag you want to test:

#! perl
use strict;
use warnings;

use constant
{
    FLAG_DELETED     => 0x0001,
    FLAG_DRAFT       => 0x0002,
    FLAG_SEEN        => 0x0004,
    FLAG_RECENT      => 0x0008,
    FLAG_FLAGGED     => 0x0010,
    FLAG_ANSWERED    => 0x0020,
    FLAG_SAVED       => 0x0040,
    FLAG_MDNSENT     => 0x0080,
    FLAG_STTPENDING  => 0x0100,
    FLAG_FAVOURITE   => 0x0200,
    FLAG_NOTIFY      => 0x0400,
    FLAG_STTPRESENT  => 0x0800,
    FLAG_STTCOMPLETE => 0x1000,
};

my  $filename  = 'mymessage.1004';
my ($flags)    = $filename  =~ / \. ([0-9a-fA-F]+) $ /x;
    $flags     = hex $flags;
my  $favourite = $flags & FLAG_FAVOURITE;

print "\nIn file '$filename', the FAVOURITE flag is ",
      ($favourite ? 'SET' : 'NOT SET'), "\n";

[download]

Output:

12:53 >perl 610_SoPW.pl

In file 'mymessage.1004', the FAVOURITE flag is NOT SET

12:57 >

[download]

Update: Fixed the regular expression to handle all hexadecimal digits. Thanks to jwkrahn, below.

Hope that helps,

Athanasius <°(((>< contra mundum Iustus alius egestas vitae, eros Piratica,

In reply to Re: How do I test if a bit has been set in a bitstring by Athanasius
in thread How do I test if a bit has been set in a bitstring by willk1980

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