Leeeeeeeeeeeeeeeeeeeeets BENCHMARK!

use Benchmark qw(:all);
                                                                      
+          
timethese(
    100,
    {
        'By File Size' => sub {
            open XLSFILE, "x";
            my $xlsdata = do { local $/ = \-s (XLSFILE); <XLSFILE> };
        },
        'Plain Slurp' => sub {
            open XLSFILE, "x";
            my $xlsdata = do { local $/; <XLSFILE> };
                                                                      
+          
        },
    }
);
[download]

Where "x" is 22Mb:

By File Size: 11 wallclock secs ( 7.54 usr +  3.11 sys = 10.65 CPU) @ 
+ 9.39/s (n=100)
Plain Slurp: 11 wallclock secs ( 8.50 usr +  2.95 sys = 11.45 CPU) @  
+8.73/s (n=100)
[download]

It appears that using the file size is a nats cock faster, which is as I would expect as the traditional slurp will have to go looking for the end of the file.

/J\