c:\@Work\Perl\monks>perl -wMstrict -le
"my $s = 'foo bar baz';
 $s =~ m{ (foo) \s* (bar) \s* (baz) }xms;
 print qq{A:  '$1'  '$2'  '$3'};
 ;;
 $s =~ m{ (xyzzy) }xms;
 print qq{B:  '$1'  '$2'  '$3'};
 ;;
 $s =~ m{ (b \w*) }xms;
 print qq{C:  '$1'  '$2'  '$3'};
"
A:  'foo'  'bar'  'baz'
B:  'foo'  'bar'  'baz'
Use of uninitialized value $2 in concatenation (.) or string at -e line 1.
Use of uninitialized value $3 in concatenation (.) or string at -e line 1.
C:  'bar'  ''  ''