# Had to add `not defined $word` to handle the special case
# during the first time through the loop. Very Ugly!
# Had to duplicate code `$word !~ /^\s*$/` to prevent the
# final ENTER from printing "You entered ''" as it exits
# the loop.
my $word;
while ( ( not defined $word ) or ( $word !~ /^\s*$/ ) ) {
   print 'Please enter a word: ';
   chomp($word = <STDIN>);
   if ( $word !~ /^\s*$/ ) {
       print "You entered '$word'\n";
   }
}