our @results;

/
   ... The work ...

   (?{ push @results, ... })
   (?!)  # Backtrack to find next result.
/x;

##</code><code>##

"abcde"=~/.*?(.)(?{print $1,"\n"})[0]/;   #produce : abcde
"abcde"=~/.*?(.)(?{print $1,"\n"})0/;     #nothing