I don't get such a large difference, but then, I don't muddy the waters by using subs or by calling external programs. 
use warnings 'all';
use strict;

use Benchmark 'cmpthese';

$::unc = '\\\\server_name\\sys_share';

cmpthese -5 => {
    blackadder => 'my $tmp =  $::unc;
                      $tmp =~ s/^\W*\w+//;
                      $server = $&;
                      $server =~ s/^\W+//;',
    theorbtwo  => '$::unc =~ m/^\\\\\\\\([^\\\\]+)\\\\/;  # Urgle.
                   my $server = $1;',
};
__END__

Name "main::unc" used only once: possible typo at bench line 6.
Benchmark: running blackadder, theorbtwo for at least 5 CPU seconds...
blackadder:  5 wallclock secs ( 5.08 usr +  0.00 sys =  5.08 CPU) @ 76
+238.39/s (n=387291)
 theorbtwo:  6 wallclock secs ( 5.07 usr +  0.00 sys =  5.07 CPU) @ 97
+024.65/s (n=491915)
              Rate blackadder  theorbtwo
blackadder 76238/s         --       -21%
theorbtwo  97025/s        27%         --

[download]
The reasonable small difference is what I expect. $& isn't as costly as it used to be, and since the blackadder code only has two regexes, you pay the price twice, compared to one for theorbtwo (due to the parens). The larger difference is that blackadder has to _copy_ the string, while that doesn't happen by theorbtwo.

Abigail

In reply to Re: Unfortunately benchmarking things with $& isn't easy... by Abigail-II
in thread Obtaining server name from UNC path by blackadder

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