# THIS doesnt mean \\server_name\sys_share it means \server_name\sys_share
$unc = '\\server_name\sys_share'; 

# and then you remove the leading "\" and trailing "\sys_share" before the benchmark even starts!
$unc =~ s/^\W*\w+//;
$server = $&;
$server =~ s/^\W+//;
# None of the regexes in the benchmark will match anymore (in a meaningful way)

##</code><code>##

#!perl
use warnings;
use Benchmark;

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

my $re = Benchmark::timethese(-5,
	{
		blackadder => sub {
			$lunc = $unc;
			$lunc =~ s/^\W*\w+//;
			$server = $&;
			$server =~ s/^\W+//;
		},
		theorbtwo => sub {
			$unc =~ m/^\\\\([^\\]+)\\/;
			$server = $1;
			}
	}
);
Benchmark::cmpthese($re);
__END__
Benchmark: running blackadder, theorbtwo, each for at least 5 CPU seconds...
blackadder:  6 wallclock secs ( 5.12 usr +  0.00 sys =  5.12 CPU) @ 131371.90/s (n=673281)
 theorbtwo:  5 wallclock secs ( 5.34 usr +  0.00 sys =  5.34 CPU) @ 190423.65/s (n=1017624)
               Rate blackadder  theorbtwo
blackadder 131372/s         --       -31%
theorbtwo  190424/s        45%         --

##</code><code>##

# benchmark saw ampersand -- BlackAdder
use strict;
use warnings;
use Benchmark qw(timethis);
use Data::Dumper;

my $count=$ARGV[0] || -1;
my $unc  =$ARGV[1] || '\\\\server_name\\sys_share';
print "Matching $unc for $count\n";
print Dumper(timethis($count,sub {
				  my $lunc = $unc;
				  $lunc =~ s/^\W*\w+//;
				  (my $server = $&)=~ s/^\W+//;
				  $server
				  },'blackadder'
));

##</code><code>##

# benchmark saw ampersand -- theorbtwo
use strict;
use warnings;
use Benchmark qw(timethis);
use Data::Dumper;

my $count=$ARGV[0] || -1;
my $unc  =$ARGV[1] || '\\\\server_name\\sys_share';
print "Matching $unc for $count\n";
print Dumper(timethis($count,sub {
				  $unc =~ m/^\\\\([^\\]+)\\/;
				  $1;
				}, 'theorbtwo'
));

##</code><code>##

use Benchmark 'cmpthese';
use Data::Dumper;

sub run_bm($){
	my $str=shift;
	my $h;
	$str=~s/\A(.*)\$VAR1 =/$h=$1;''/se;
	print $h;
	my $v=eval($str);
	die $@ if $@;
	$v
}

my $opts='-5 \\\\foo\\bar\\baz.exe;

my $hash={
          blackadder => run_bm(`perl bm_blackadder.pl $opts`),
          theorbtwo  => run_bm(`perl bm_theorbtwo.pl $opts`),
         };
cmpthese($hash);
__END__

##</code><code>##

Matching \\foo\bar\baz.exe for -5
blackadder:  6 wallclock secs ( 5.22 usr +  0.00 sys =  5.22 CPU) @ 135204.60/s (n=705768)
Matching \\foo\bar\baz.exe for -5
 theorbtwo:  6 wallclock secs ( 5.17 usr +  0.00 sys =  5.17 CPU) @ 367160.48/s (n=1898954)
               Rate blackadder  theorbtwo
blackadder 135205/s         --       -63%
theorbtwo  367160/s       172%         --