我想在正则表达式括号中使用一个变量，
但它似乎不起作用。
$ echo 'abcabcabc' | awk '{ sub(/(abc){2}/,"XXX"); print }'
XXXabc
# this is not a correct result.
$ echo 'abcabcabc' | awk '{ i=2; sub(/(abc){i}/,"XXX"); print }'
abcabcabc
$ echo 'abcabcabc' | awk '{ if (/(abc){3}/) print "ok" }'
ok
# this does not work correctly.
$ echo 'abcabcabc' | awk '{ i=3; if (/(abc){i}/) print "ok" }'