c:\@Work\Perl\monks\perl -wMstrict -le
"my $file = qq{\x0f\xf0\xff};
 my $data = unpack( 'H*', $file );
 my $count =()= $data =~ /ff/g;
 print $count;
"
2

##</code><code>##

c:\@Work\Perl\monks>perl -wMstrict -le
"my $file = qq{\x0f\xf0\xff};
 my $count =()= $file =~ /\xff/g;
 print $count;
"
1

##</code><code>##

c:\@Work\Perl\monks>perl -wMstrict -le
"my $file = qq{\x0f\xf0\xff};
 my $count = $file =~ tr/\xff//;
 print $count;
"
1