D'oh! I optimized the split but not the regex :( That'll teach me to be careless. For honesty's sake:

timethese(1000000, { 
    Regex  => '$a=$1 if $myvar   =~ /^[^,]+,([^,]+)/',
    Split1 => '$result = (split /,/, $myvar)[1]',
    Split2 => '$result = (split /,/, $myvar, 4)[1]',
    Split3 => '$result = (split /,/, $myvar, 3)[1]'
});

Benchmark: timing 1000000 iterations of Regex, Split1, Split2, Split3.
+..
     Regex: 14 wallclock secs (14.12 usr +  0.00 sys = 14.12 CPU)
    Split1: 17 wallclock secs (16.54 usr +  0.00 sys = 16.54 CPU)
    Split2: 16 wallclock secs (16.75 usr +  0.00 sys = 16.75 CPU)
    Split3: 14 wallclock secs (13.02 usr +  0.00 sys = 13.02 CPU)
[download]

I'm going to cry myself to sleep tonight.

Curiously, though, it was the null assignments that appeared to be killing the efficiency ($a=$1, $b=$2, $c=$3, $d=$4) much more than the unoptimized regex. Hmmm....

Cheers,
Ovid