import re
line = "GeneralBKT_n24_-e_dee_testcaseid_blt12_0001_s3_n4"
for id in re.finditer(r'testcaseid_([^_]+_[^_]+)', line):
print(id.group(1))
aW1wb3J0IHJlCgpsaW5lID0gIkdlbmVyYWxCS1RfbjI0Xy1lX2RlZV90ZXN0Y2FzZWlkX2JsdDEyXzAwMDFfczNfbjQiCgpmb3IgaWQgaW4gcmUuZmluZGl0ZXIocid0ZXN0Y2FzZWlkXyhbXl9dK19bXl9dKyknLCBsaW5lKToKCXByaW50KGlkLmdyb3VwKDEpKQo=