Another way is to use a POSIX character class (perlre, perlreref):

use warnings;
use strict;

my $line = 'M6608BBBBQYMNM1000.data:0x4443018d D debug_mode';

if ($line =~ /(0x[[:xdigit:]]+)/) {
    print "$1\n";
}

__END__

0x4443018d
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