import re
p = re.compile(r'@\w*handle\w*')
test_str = "@handle what is your problem?\nwhat is your problem @handle?\n@123handle what is your problem @handle123?\n"
print(p.findall(test_str))
aW1wb3J0IHJlCnAgPSByZS5jb21waWxlKHInQFx3KmhhbmRsZVx3KicpCnRlc3Rfc3RyID0gIkBoYW5kbGUgd2hhdCBpcyB5b3VyIHByb2JsZW0/XG53aGF0IGlzIHlvdXIgcHJvYmxlbSBAaGFuZGxlP1xuQDEyM2hhbmRsZSB3aGF0IGlzIHlvdXIgcHJvYmxlbSBAaGFuZGxlMTIzP1xuIgpwcmludChwLmZpbmRhbGwodGVzdF9zdHIpKQ==