Really, then what is wrong with my benchmark? 

#! perl -slw
use strict;
use Benchmark qw[cmpthese];

my @tests = map{
    my $s = 'N' x $_;
    ( "${s}S${s}S", "${s}S${s}S${s}", "S${s}S${s}" )
} map{ $_ * 10 } 1 .. 100;

@$_ = @tests for \ our( @a, @b, @c, @d );

cmpthese 10, {
    a=>q[ s[^N*(.*?)N*$][$1]    for @a ],
    b=>q[ s[N*$][] and s[^n*][] for @b ],
    c=>q[ s[N*$][] and s[^n*][] for @c ],
    d=>q[ s[^N*(.*?)N*$][$1]    for @d ],
};

__END__
P:\test>junk
    Rate    b    c    a    d
b 6.10/s   --  -1% -27% -28%
c 6.15/s   1%   -- -26% -27%
a 8.31/s  36%  35%   --  -1%
d 8.42/s  38%  37%   1%   --

[download]

In reply to Re^3: Removing Flanking "N"s in a DNA String by BrowserUk
in thread Removing Flanking "N"s in a DNA String by monkfan

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