. "$BST_LIB"
require gawk gawk/present
check_out gawk/arith    "42"      gawk "BEGIN{print 6*7}"
check_out gawk/fields   "beta"    sh -c "echo 'alpha beta gamma' | gawk '{print \$2}'"
check_out gawk/gsub     "X.X.X"   sh -c "echo 'a.a.a' | gawk '{gsub(/a/,\"X\"); print}'"
check_out gawk/nr       "count=3" sh -c "printf '1\n2\n3\n' | gawk 'END{print \"count=\" NR}'"