:local fileName "iplist.txt"
:local fileContents [/file get $fileName contents]
:local addressListName "MyAddressList" 

:foreach ip in=$fileContents do={
    /ip firewall address-list add list=$addressListName address=$ip
}

{
    :local filebody [/file/get iplist.txt contents]
    :local addressListName "MyAddressList"
    :local expire 1h
    
    :foreach ip in=[ :deserialize [:tolf $filebody] delimiter="\n" from=dsv options=dsv.plain ] do={
        /log debug "adding $ip to $addressListName"
        :if ([:tostr $ip] != "0.0.0.0") do={
             :onerror e in={
                  /ip firewall address-list add list=$addressListName address=$ip timeout=$expire
              } do={/log debug "skipping $ip ($e)"}
        }
    }
}

# Variables
:local url "https://myurl/blocklist.txt"
:local fileName "blocklist.txt"
:local addressListName "blocklist"
:local filebody
:local delayTime 5s

# Download the specified file
/tool fetch url=$url mode=https dst-path=$fileName

# 5 second delay
:delay $delayTime

# Remove all addresses from the specified list
/ip firewall address-list remove [find list=$addressListName]

# Reads the contents of the file and stores it in the local variable filebody
:set filebody [/file get $fileName contents]

# Iterate over each IP from the file contents and add it to the specified list of addresses
:foreach ip in=[:deserialize $filebody delimiter="\n" from=dsv options=dsv.plain] do={
    :put $ip
    /ip firewall address-list add list=$addressListName address=$ip
}

# Command to remove the file
/file remove $fileName

1.1.1.1
2.2.2.2

 > :put [:deserialize [/file/get iplist.txt contents] delimiter="\n" from=dsv options=dsv.plain]
1.1.1.1;2.2.2.2;
 > :put [:deserialize [/file/get iplist.txt contents] delimiter="\r\n" from=dsv options=dsv.plain]
1.1.1.1;2.2.2.2;
 > :put [:deserialize [/file/get iplist.txt contents] delimiter="." from=dsv options=dsv.plain]
1;1;1;1;2;2;2;2;
 > :put [:deserialize [/file/get iplist.txt contents] delimiter="foo" from=dsv options=dsv.plain]
1.1.1.1;2.2.2.2;

:put [:deserialize "test\rte<!>st\ntest" delimiter="<!>" from=dsv options=dsv.plain]
test;te;st;test

:put [:serialize to=json options=json.pretty [:deserialize "test\rte<!>st\ntest" delimiter="<!>" from=dsv options=dsv.plain]] 
[
    [
        "test"
    ],
    [
        "te",
        "st"
    ],
    [
        "test"
    ]
]

:put ([:deserialize "test\rte<!>st\ntest" delimiter="<!>" from=dsv options=dsv.plain]->1->1) 
st