('x' x 90).' '.('x' x 10)
  
              Rate stevenmay  ikegami2  ikegami1
stevenmay 256955/s        --      -35%      -48%
ikegami2  394568/s       54%        --      -19%
ikegami1  490119/s       91%       24%        --


('x' x 10).' '.('x' x 90)

              Rate stevenmay  ikegami2  ikegami1
stevenmay 102399/s        --      -13%      -19%
ikegami2  118154/s       15%        --       -7%
ikegami1  126866/s       24%        7%        --

##</code><code>##

('x' x 99)

               Rate  ikegami1 stevenmay  ikegami2
ikegami1   771011/s        --      -81%      -83%
stevenmay 4071762/s      428%        --      -12%
ikegami2  4620312/s      499%       13%        --

##</code><code>##

use strict;
use warnings;

use Benchmark qw( cmpthese );

my %tests = (
   stevenmay => <<'__EOI__',
my $string = $input;
if ( $string and length $string > 100 ){
   $string = substr( $string, 0, 100);
   my ($tmp) = $string =~ /(.+)\s.*?$/s; # last space if possible
   $tmp or ($tmp) = $string =~ /(.+)\W.*?$/s; # bust on last non-word
   $tmp and $string = $tmp;
}
__EOI__

   ikegami1 => <<'__EOI__',
my ($string) = $input =~ /^(.{0,100})(?!\S)/s;
__EOI__

   ikegami2 => <<'__EOI__',
my $string = $input;
if (length($string) > 100) {
   $string =~ s/^(.{0,100})(?!\S)\K.*//s
}
__EOI__
);

$_ = 'use strict; use warnings; our $input; '.$_.' 1'
   for values(%tests);

{
   local our $input = ('x' x 90).' '.('x' x 10);
   cmpthese(-1, \%tests);
} {
   local our $input = ('x' x 10).' '.('x' x 90);
   cmpthese(-1, \%tests);
} {
   local our $input = ('x' x 99);
   cmpthese(-1, \%tests);
}