unpackM => sub { # Multi-line unpack suggested by LanX
       seek $inFH, 0, 0;

       my $buffer     = <$inFH>;
       my $lineLen    = length $buffer;
       my $nLines     = 500;
       my $chunkSize  = $lineLen * $nLines;

       seek $inFH, 0, 0;

       my $retStr;
       my $fmt = qq{(x${offset}ax@{ [ $lineLen - $offset - 1 ] })*};
       while ( my $bytesRead = read $inFH, $buffer, $chunkSize )
       {
           $retStr .= join q{}, unpack $fmt, $buffer;
       }

       return \ $retStr;
   },

##</code><code>##

ok 1 - brutish
ok 2 - pushAoA
ok 3 - regex
ok 4 - rsubstr
ok 5 - seek
ok 6 - split
ok 7 - substr
ok 8 - unpack
ok 9 - unpackM
          Rate pushAoA brutish  split   seek regex unpack substr rsubstr unpackM
pushAoA 1.14/s      --    -32%   -60%   -61%  -90%   -97%   -98%    -98%    -98%
brutish 1.68/s     47%      --   -41%   -43%  -86%   -95%   -96%    -97%    -97%
split   2.83/s    148%     69%     --    -3%  -76%   -92%   -94%    -94%    -95%
seek    2.93/s    157%     75%     4%     --  -76%   -92%   -94%    -94%    -95%
regex   12.0/s    952%    618%   325%   310%    --   -66%   -75%    -75%    -80%
unpack  35.1/s   2970%   1993%  1140%  1097%  192%     --   -27%    -28%    -43%
substr  47.8/s   4081%   2751%  1588%  1530%  297%    36%     --     -3%    -22%
rsubstr 49.1/s   4193%   2827%  1634%  1574%  308%    40%     3%      --    -20%
unpackM 61.1/s   5247%   3546%  2059%  1985%  408%    74%    28%     25%      --
1..9

##</code><code>##

   ANDmask => sub { # Multi-line AND mask by johngg
       seek $inFH, 0, 0;

       my $buffer     = <$inFH>;
       my $lineLen    = length $buffer;
       my $nLines     = 500;
       my $chunkSize  = $lineLen * $nLines;

       seek $inFH, 0, 0;

       my $retStr;
       my $mask
          = qq{\x00} x ${offset}
          . qq{\xff}
          . qq{\x00} x ( $lineLen - $offset - 1 );
       $mask x= $nLines;
       while ( my $bytesRead = read $inFH, $buffer, $chunkSize )
       {
           ( my $anded = $buffer & $mask ) =~ tr{\x00}{}d;
           $retStr .= $anded;
       }

       return \ $retStr;
   },

##</code><code>##

ok 1 - ANDmask
ok 2 - brutish
ok 3 - pushAoA
ok 4 - regex
ok 5 - rsubstr
ok 6 - seek
ok 7 - split
ok 8 - substr
ok 9 - unpack
ok 10 - unpackM
          Rate pushAoA brutish split  seek regex unpack substr rsubstr unpackM ANDmask
pushAoA 1.11/s      --    -35%  -61%  -62%  -91%   -97%   -98%    -98%    -98%    -99%
brutish 1.71/s     55%      --  -39%  -41%  -86%   -95%   -96%    -96%    -97%    -98%
split   2.82/s    155%     65%    --   -3%  -77%   -92%   -94%    -94%    -95%    -97%
seek    2.91/s    163%     70%    3%    --  -76%   -92%   -94%    -94%    -95%    -97%
regex   12.3/s   1010%    617%  336%  322%    --   -65%   -74%    -75%    -79%    -88%
unpack  35.0/s   3060%   1943% 1141% 1102%  185%     --   -25%    -27%    -40%    -67%
substr  46.9/s   4137%   2638% 1564% 1512%  282%    34%     --     -3%    -20%    -55%
rsubstr 48.2/s   4254%   2714% 1610% 1556%  292%    38%     3%      --    -18%    -54%
unpackM 58.7/s   5194%   3321% 1979% 1914%  377%    68%    25%     22%      --    -44%
ANDmask  105/s   9407%   6045% 3634% 3517%  757%   201%   124%    118%     80%      --
1..10