# Instead of using `not defined $word`, I force
# non-whitespace into $word.
# Still very ugly.
# Still had to duplicate code `$word !~ /^\s*$/`
my $word = 'JunkToPreventFailingTheFirstLoop';
while ( $word !~ /^\s*$/ ) {
   print 'Please enter a word: ';
   chomp($word = <STDIN>);
   if ( $word !~ /^\s*$/ ) {
       print "You entered '$word'\n";
   }
}