c:\@Work\Perl\monks>perl -wMstrict -le
"my $s = 'one two three four';
 ;;
 $s =~ m{
   \A
   (?<save>  \w+) \s+
   (?<this>  \w+) \s+
   (?<for>   \w+) \s+
   (?<later> \w+) \s*
   \z
   }xms;
 print join '-', @+{ qw(save this for later) };
 ;;
 $s = 'fee fie foe fum';
 ;;
 $s =~ m{
   (?{ print join '==', @+{ qw(save this for later) } })
   \A
   (?<save>  \w+) \s+
   (?<this>  \w+) \s+
   (?<for>   \w+) \s+
   (?<later> \w+) \s*
   \z
   }xms;
 print join '+++', @+{ qw(save this for later) };
"
one-two-three-four
Use of uninitialized value in join or string at (re_eval 1) line 1.
Use of uninitialized value in join or string at (re_eval 1) line 1.
Use of uninitialized value in join or string at (re_eval 1) line 1.
Use of uninitialized value in join or string at (re_eval 1) line 1.
======
fee+++fie+++foe+++fum