package require ip

proc IPv4toIPv6 {addr} {
    if {![ip::is ipv4 $addr]} {
        error "need an IPv4 address"
    }
    set raw [ip::toInteger $addr]
    return [ip::normalize [format "::FFFF:%04x:%04x" [expr {$raw >> 16}] [expr {$raw & 0xFFFF}]]]
}

set v6 [IPv4toIPv6 10.24.13.91]
puts "Full address: $v6"
# Full address: 0000:0000:0000:0000:0000:ffff:0a18:0d5b
puts "Abbreviated: [ip::contract $v6]"
# Abbreviated: ::ffff:a18:d5b