[Boston.pm] Is it really that fast?

[Andrew Stanley]

I wrote a bit of  code that I was concerned about the speed of.  It looks
like:

        return map {
                my $x = $_;
                $x =~ s/(?<!^)(')(?!$)/$1$1/g;
                $x;
        } @_;

So, I benchmarked it, and got:

Benchmark: timing 1000000 iterations of lookaround...
lookaround:  0 wallclock secs ( 0.48 usr +  0.00 sys =  0.48 CPU) @ 
2083333.33/s (n=1000000)

I thought the (?<!) and (?!) were expensive, since I need to stop, look
behind, look ahead, and then move on -- am I wrong?  The actual
benchmarking code follows.

Cheers,

-Andrew

timethese(1000000, { 
        lookaround => q{ 
                map {
                        my $x = $_;
                        $x =~ s/(?<!^)(')(?!$)/$1$1/g;
                        $x;
                } @arr;
             }
        } );


Andrew Stanley
http://www.cs.uml.edu/~astanley/