cmpthese ( COUNT, CODEHASHREF, [ STYLE ] )

Optionally calls timethese(), then outputs comparison chart. This:
    cmpthese( -1, { a => "++\$i", b => "\$i *= 2" } ) ;
outputs a chart like:
           Rate    b    a
    b 2831802/s   -- -61%
    a 7208959/s 155%   --