Code below shows my minor tweaks, idnopheq, to your neat snippet.

Line 12 rejects $mask if any octet(s) are other than 1 to 3 digits.   Somewhat redundant, since you already check for > 255 at line 20.

Line 22y3 allows the sub to pass the valid octet of 252, which happens to not be divisable by 8.   Although you may have left that out on purpose, since a 30bit mask would normally be used only with point-to-point WAN links.

I've not used them yet myself, but modules like Net::Netmask, Net::IPv4Addr, Network::IPv4Addr, NetAddr::IP, and Tie::NetAddr::IP might be worth looking at.
    cheers,
    Don
    striving toward Perl Adept
    (it's pronounced "why-bick") 

1:  # sub validateMask
2:  #
3:  #     takes a dotted-decimal IP mask
4:  #
5:  #     returns 1 if the mask is valid
6:  #     returns undef if not
7:  #
8:  
9:  sub validateMask {
10:   my $mask       = shift;
11:   my $net        = 0;
12:   return
12:     unless $mask =~/^(\d{1,3})\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})$/;
12y:                                   # accept only 1 to 3 digit octe
+ts in above regex
14:   foreach ( split ( /\./, $mask ) ) {
15:     if (
16:     $net    == 1
17:     &&
18:     $_      != 0
19:     )                 { return; }
20:     if ( $_      > 255 ) { return; }
21:     if ( $_     == 255 ) { next;   }
22:     if (
22y1:   $_ % 8 != 0                       # if an octet mod 8 isn't 0,
+ bad mask
22y2:   &&
22y3:   $_ != 252                         # 255 is valid octet, but oc
+tet mod 8 isn't 0
22y4:   )   { return; }
23:     $net = 1;
24:     next;
25:   }
26:   return 1;
27: }

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In reply to Re: validateMask (regex tweak, 30bit mask, CPAN modules) by ybiC
in thread validateMask by idnopheq

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