You could accumulate words into a hash:

use warnings;
use strict;
use Data::Dumper;
$Data::Dumper::Sortkeys = 1;

my %words;
while (<DATA>) {
    $words{$_}++ for split;
}
print Dumper(\%words);

__DATA__
the the the and me
ok big dog me
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Prints:

$VAR1 = {
          'and' => 1,
          'big' => 1,
          'dog' => 1,
          'me' => 2,
          'ok' => 1,
          'the' => 3
        };
[download]

See also:

• split
• perlintro
• Data::Dumper