[0] Perl> for(2..6){ 
    %a =(); %b = 1.."1e$_"; 
    cmpthese -1, { 
        A=>q[ for(1 .. 10000){     if( %a ){ 1; } } ], 
        B=>q[ for(1 .. 10000){ unless( %b ){ 1; } } ] 
    } 
};;
    Rate    B    A
B 72.0/s   -- -90%
A  726/s 908%   --
    Rate    B    A
B 72.6/s   -- -90%
A  736/s 914%   --
    Rate    B    A
B 70.5/s   -- -91%
A  751/s 965%   --
    Rate    B    A
B 69.5/s   -- -91%
A  759/s 992%   --
    Rate    B    A
B 71.5/s   -- -90%
A  715/s 900%   --

[0] Perl> for(2..6){ 
    %a =(); %b = 1.."1e$_"; 
    cmpthese -1, { 
        A=>q[ for(1 .. 10000){ unless( %a ){ 1; } } ], 
        B=>q[ for(1 .. 10000){     if( %b ){ 1; } } ] 
    } 
};;
    Rate    B    A
B 75.9/s   -- -89%
A  709/s 834%   --
    Rate    B    A
B 73.7/s   -- -90%
A  730/s 890%   --
    Rate    B    A
B 72.7/s   -- -90%
A  747/s 928%   --
    Rate    B    A
B 71.5/s   -- -90%
A  725/s 914%   --
    Rate    B    A
B 70.6/s   -- -90%
A  708/s 903%   --