my $testvar = "Bob Q Smith bsmith 00001234567 5/1/00 12:00:00";

$testvar =~ s/
              \s           # a whitespace character (space, tab, etc)
              (            # Capture to $1
                \w+        #    one or more word characters (e.g. bsmith)
              )
              \s           # a whitespace character
              (            # Capture to $2
                \d+        #    one or more digits
              )
              \s           # a whitespace character
            /,$1,$2,/x;