Code Golf: Quickly Build List of Keywords from Text, Including # of Instances

Answer 1

Perl in only 43 characters.

perl -MYAML -anE'$_{$_}++for@F;say Dump\%_'

Here is an example of it's use:

echo a a a b b c  d e aa | perl -MYAML -anE'$_{$_}++for@F;say Dump \%_'

---
a: 3
aa: 1
b: 2
c: 1
d: 1
e: 1

If you need to list only the lowercase versions, it requires two more characters.

perl -MYAML -anE'$_{lc$_}++for@F;say Dump\%_'

For it to work on the specified text requires 58 characters.

curl http://sampsonresume.com/labs/c.txt |
perl -MYAML -F'\W+' -anE'$_{lc$_}++for@F;END{say Dump\%_}'

real    0m0.679s
user    0m0.304s
sys     0m0.084s

Here is the last example expanded a bit.

#! perl
use 5.010;
use YAML;

while( my $line = <> ){
  for my $elem ( split '\W+', $line ){
    $_{ lc $elem }++
  }
  END{
    say Dump \%_;
  }
}