comment on

I think all the corner cases in IPv6 addresses are likely to make you crazy if you try to do the whole problem in an RE. You could try the is_ipv6 function here:

my $quad     = "[0-9a-fA-F]{0,4}";
my $ipv6addr = "(?:$quad:){2,7}$quad";

sub is_ipv6 {
    local $_ = $_[0];
    return 0
      unless m{^$ipv6addr(?:/(\d+))?$};
    my $mask = defined($1) ? $1 : 128;
    # in 5.10: my $mask = $1 // 128;
    return 0
      if /:::/
      or /::.*::/
      or not /::/ and 7 != tr/:/:/;
    return ( 0 <= $mask and $mask <= 128 );
}
[download]

But you might be better off to just go ahead and try to convert the address with NetAddr::IP -> new6, and see if the result is true. A quick and dirty test comparing the two approaches...

use warnings;
use strict;
use NetAddr::IP;

my $quad     = "[0-9a-fA-F]{0,4}";
my $ipv6addr = "(?:$quad:){2,7}$quad";

sub is_ipv6 {
    local $_ = $_[0];
    return 0
      unless m{^$ipv6addr(?:/(\d+))?$};
    my $mask = defined($1) ? $1 : 128;
    # in 5.10: my $mask = $1 // 128;
    return 0
      if /:::/
      or /::.*::/
      or not /::/ and 7 != tr/:/:/;
    return ( 0 <= $mask and $mask <= 128 );
}

while (<DATA>) {
    chomp;
    printf "%-25s ", $_;
    my $addr = NetAddr::IP -> new6 ($_);
    $addr ||= "";
    printf "%-25s ", $addr;
    print is_ipv6($_) ? "yes\n" : "no\n";
}
__DATA__
::
::/0
::1/128
1::/64
:
:/96
2001:1::/64
2001:0:6:4003::/64
2001::12/128
2001::15/0
2001::15/-1
2001::15/129
20012::15/96
2001:1:::2/96
2001::1::2/96
2001::1:2::3/96
2001:2:3:4:5:6:7/48
2001:2:3:4::6:7/48
2001:2:3:4:5:6:7:8/64
2001:2:3:4:5:6:7:8:9/96
2001:2:3:4::6:7:8:9/96
[download]

prints the following:

::                        0:0:0:0:0:0:0:0/128       yes
::/0                      0:0:0:0:0:0:0:0/0         yes
::1/128                   0:0:0:0:0:0:0:1/128       yes
1::/64                    1:0:0:0:0:0:0:0/64        yes
:                                                   no
:/96                                                no
2001:1::/64               2001:1:0:0:0:0:0:0/64     yes
2001:0:6:4003::/64        2001:0:6:4003:0:0:0:0/64  yes
2001::12/128              2001:0:0:0:0:0:0:12/128   yes
2001::15/0                2001:0:0:0:0:0:0:15/0     yes
2001::15/-1                                         no
2001::15/129                                        no
20012::15/96                                        no
2001:1:::2/96                                       no
2001::1::2/96                                       no
2001::1:2::3/96                                     no
2001:2:3:4:5:6:7/48                                 no
2001:2:3:4::6:7/48        2001:2:3:4:0:0:6:7/48     yes
2001:2:3:4:5:6:7:8/64     2001:2:3:4:5:6:7:8/64     yes
2001:2:3:4:5:6:7:8:9/96                             no
2001:2:3:4::6:7:8:9/96                              no
[download]

In reply to Re: Regex host portion of IPv6 address by quester
in thread Regex host portion of IPv6 address by ewhitt

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