sub nonblank {
    return grep { /\S/ } @_
}

print nonblank('foo'); # list context through print()
print $_ for nonblank('foo'); # explicit list context

my $temp= nonblank('foo'); # scalar context
print $temp; # still scalar

( $temp)= nonblank('foo'); # list context, discarding all but the first element
print $temp; # First element of that list

   $temp= (nonblank('foo'))[0]; # Scalar context in assignment, but we only take the first element explicitly
print $temp;