$ openssl asn1parse -i < [BASIC CONSTRAINTS]
    0:d=0  hl=2 l=   7 cons: SEQUENCE          
    2:d=1  hl=2 l=   1 prim:  BOOLEAN           :255
    5:d=1  hl=2 l=   2 prim:  INTEGER           :0100
-----BEGIN BASIC CONSTRAINTS-----
MAcBAf8CAgEA
-----END BASIC CONSTRAINTS-----