c:\@Work\Perl>perl -wMstrict -le
"my $record = do {
   my $id    = qr{ \d+ }xms;
   my $name  = qr{ [[:upper:]] [[:lower:]]+ }xms;
   my $first = $name;
   my $last  = $name;
   my $age   = qr{ \d+ }xms;
   qr{
     \A  ID=    ($id)
     \s+ First= ($first) \s+ Last= ($last)
     \s+ AGE=   ($age)
     \z
     }xms;
   };
 ;;
 for my $rec ('ID=1 First=John Last=Doe AGE=42', @ARGV) {
   my ($id, $first_name, $last_name, $age) = $rec =~ m{ $record }xms
     or die qq{malformed record: '$rec'};
   print qq{id '$id'  first '$first_name'  last '$last_name'  age '$age'};
   }
"  "ID=2  First=Joe  Last=42  AGE=Doe"
id '1'  first 'John'  last 'Doe'  age '42'
malformed record: 'ID=2  First=Joe  Last=42  AGE=Doe' at -e line 1.