Extract Lines when Column K is empty with AWK/Perl

Question

I have data that looks like this:

foo 78 xxx
bar    yyy
qux 99 zzz
xuq    xyz

They are tab delimited. How can I extract lines where column 2 is

Answer 1

grep -e '^.*\t\t.*$' myfile.txt

Will grep each line consisting of characters-tab-tab-characters (nothing between tabs).