testdir/t.substr - platform/external/one-true-awk - Git at Google

 substr($2, 1, 1) ~ /[abc]/
 substr($2, length($2)) !~ /[a-z]/
 substr($2, length($2)) ~ /./
	substr($2, 1, 1) ~ /[abc]/
	substr($2, length($2)) !~ /[a-z]/
	substr($2, length($2)) ~ /./