github.com/benhoyt/goawk@v1.8.1/testdata/t.set0 (about)

     1  {$0 = $1; print; print NF, $0; print $2}
     2  {$(0) = $1; print; print NF, $0; print $2}
     3  { i = 1; $(i) = $i+1; print }