use strict;
use warnings;

my @strings = (
  "____\n",   "__ __\n",  "__X __\n",
  "__Z__\n",  "__\n__\n", "__^__\n",
  "_____\n",  "________\n",
); 


foreach my $string ( @strings ) {
  print "<<$string>>\n";
  if( $string =~ m/__(\S+?)__/ ) {
    print "\tNon-Greedy -- Match: (($1)).\n";
  }
  else {
    print "\tNon-Greedy -- No Match.\n";
  }
  if( $string =~ m/__(\S+)__/ ) {
    print "\tGreedy     -- Match: [[$1]].\n";
  }
  else {
    print "\tGreedy     -- No Match.\n";
  }
}