Help me write a good reg-exp for this text

[waxmop]

I need to parse this page and create a hash using the codes as keys and the descriptions as values.

This is a section showing what the page looks like:

Total index                                              B50001
 Crude processing (capacity)                             B5610C
 Primary & semifinished processing (capacity)            B562A3C
 Finished processing (capacity)                          B5640C
 Manufacturing ("SIC")                                   B00004
  Manufacturing (NAICS)                                  GMF
   Durable manufacturing (NAICS)                         GMFD
    Wood product                                         G321         
+    321
    Nonmetallic mineral product                          G327         
+    327
    Primary metal                                        G331         
+    331
     Iron and steel products                             G3311A2      
+    3311,2
    Fabricated metal product                             G332         
+    332
    Machinery                                            G333         
+    333

I want to build a hash that would work like this:

my $code = "GMF";

print "$code: $description_hash{$code}.\n";

That should print:

GMF: Manufacturing (NAICS).

All preceding and trailing whitespace needs to be removed from the description.

I've never been expert with regular expressions, so I'd love to see how the really smart people that hang out on this site would build that hash. Thanks in advance!