m/t([^e]*)e/, m/wri([^e]*)en/);

##</code><code>##

Benchmark: timing 300000 iterations of dotstar, negchar... on string q/tddddde/
   dotstar:  1 wallclock secs ( 1.37 usr +  0.00 sys =  1.37 CPU) @ 218658.89/s (n=300000)
   negchar:  0 wallclock secs ( 0.95 usr +  0.00 sys =  0.95 CPU) @ 315457.41/s (n=300000)
            Rate dotstar negchar
dotstar 218659/s      --    -31%
negchar 315457/s     44%      --