This was from another node, but I would like to post it as the main question. The original question was anwsered, but when benchmarking it I noticed a large difference in the speed of the operation, myself and the monk who posted the orignal question are curious as to why. Here is the code:

#!perl
use strict;
use File::Basename;
use CGI;
use Benchmark;
use Win32;

my $cgi = CGI->new();

print $cgi->header;

print "Hello World<br>";

print "DOS NAME: " . basename($0) . "<BR>";

print "ENV BASENAME: " . basename($ENV{SCRIPT_FILENAME}) . "<br>";

print "Win32 BASENAME: " . basename(Win32::GetLongPathName($0)) . "<br
+>";

timethese (100000, {
       'basename_env'   => sub { basename(Win32::GetLongPathName($0)) 
+},
       'basename_win32' => sub { basename($ENV{SCRIPT_FILENAME}) },
       'basemane_dollar0' => sub { basename($0) },
        }
);

1;
[download]

        The results 

Benchmark: timing 100000 iterations of 
    basemane_dollar0, 
    basename_env, 
    basename_win32...
basemane_dollar0:  5 wallclock secs 
    ( 3.68 usr +  0.00 sys =  3.68 CPU) @ 27203.48/s (n=100000)
basename_env: 121 wallclock secs 
    (34.99 usr + 81.07 sys = 116.06 CPU) @ 861.65/s (n=100000)
basename_win32:  5 wallclock secs 
    ( 4.24 usr +  0.00 sys =  4.24 CPU) @ 23557.13/s (n=100000)

Now I would like to know why the $ENV way is SO slow. I had expected there might be a little difference, but 10 times slower? At first I thought is was partly the hash lookup, but even when I did a sub with the string (path) instead of the hash it was still slow.