#!/usr/local/bin/perl

while(<DATA>) {
    /(\w*)/;
    $i{$1}++;
}

print "$_\n" for keys %i;

__DATA__
foo
bar
baz
qux
foo
foo
bar
baz
qux

##</code><code>##

perl -nle '/(\w*)/;$i{$1}++;print for keys %i;' words.txt