github.com/benhoyt/goawk@v1.8.1/testdata/t.match1 (about)

     1  NF > 0 && match($NF, $1) {
     2  	print $0, RSTART, RLENGTH
     3  	if (RLENGTH != length($1))
     4  		printf "match error at %d: %d %d\n",
     5  			NR, RLENGTH, RSTART >"/dev/tty"
     6  }