Catmandu::Fix::lookup

    # dictionary.csv
    # id,planet
    # 1,sun
    # 2,earth
    # 3,moon
    # values found in the dictionary.csv will be replaced
    # {foo => {bar => 2}}
    lookup(foo.bar, dictionary.csv)
    # {foo => {bar => 'earth'}}
    # values not found will be kept
    # {foo => {bar => 232}}
    lookup(foo.bar, dictionary.csv)
    # {foo => {bar => 232}}
    # in case you have a different seperator
    lookup(foo.bar, dictionary.csv, sep_char: |)
    # delete value if the lookup fails:
    lookup(foo.bar, dictionary.csv, delete: 1)
    # use a default value if the lookup fails:
    lookup(foo.bar, dictionary.csv, default: 'default value')

Catmandu::Fix, Catmandu::Fix::mapping