Re^2: Print Number With Implied Decimal Point

[kennethk]

in reply to Re: Print Number With Implied Decimal Point
in thread Print Number With Implied Decimal Point

If you want to make the regex solution run much more quickly, use Look Around Assertions in place of the capture and reinsert.

cmpthese(0, {
              substr => sub {
                  my @l = @list;
                  substr $_, -2, 0, '.' for @l;
              },
              regex => sub {
                  my @l = @list;
                  s/(..)$/.$1/ for @l;
              },
              regex2 => sub {
                  my @l = @list;
                  s/(?=..)$/./ for @l;
              },
             });

yields

         Rate substr  regex regex2
substr 73.1/s     --   -39%   -71%
regex   121/s    65%     --   -52%
regex2  250/s   242%   107%     --

Update: As per JavaFan's comment, I had a typo in my sub. Replaced s/(?=..)$/./ with s/(?=..$)/./ which returns the correct result, but at substantially poorer performance.

[JavaFan]

These numbers look too good to be true:

$_ = "9876543";
s/(?=..)$/./;
say;
__END__
9876543

You cannot actual replace a zero-width assertion.

And before benchmarking, you should always check whether you're producing the correct results. Bogus solutions noone cares for, even if they're fast.