Pretty basic problem but it's got me tearing my hear out. Short, sweet description: I'm calling a sub. At the beginning of the sub, I'm initializing a variable. The variable appears to be acting like a C static and retaining it's value between calls. Here's the code: 
use strict;

open TXT, "<masks.txt" or die "Can't open masks.txt\n";

while(<TXT>) {
    chomp;
    my @words = split(/ +/);
    print "Checking mask $words[2]\n";
    my $maskvalid = ValidateMasks($words[2]);
    print "Mask is $maskvalid\n\n";
}

sub ValidateMasks() {
    return 0 unless defined $_[0];
    my @octets = split (/\./, $_[0]);
    print "\toctets array is @octets\n";
    my $valid = 1;
    my $index = 0;
    my $flagvalue = 0;

    while($index < 4) {
        $valid = ValidateOctet($octets[$index]);
        $index++;
    }
    return $valid;

    sub ValidateOctet() {
        return 0 unless defined $_[0];  # bad if no argument passed
        return 0 unless $valid;  # return bad if any previous argument
+ is bad
        my $oc = $_[0];

        return 0 if $oc > 255;  # bad if value is above 255
        print "\tchecking octet $oc\n";
        return 1 if ($oc eq $flagvalue);  # good if equal to flag valu
+e 
            print "\t\tUnequal: oc is $oc, flagvalue is $flagvalue\n";
        return 0 if $flagvalue;  # bad if this is a second non-zero an
+d it's not equal to 255.
        $flagvalue = 255;  # All further octets after this one must be
+ 255

        # This is the first non-zero octet.
        # Should be equal to a power of 2 minus 1
        # X is a power of 2 if (X & X-1) = 0
        # $oc + 0 forces value to number vice string
        my $bitand = ($oc + 0) & ($oc + 1);
        return ( $bitand ? 0 : 1);
    }
}

[download]
And the data file: 
field1 10.1.253.11  0.0.0.0
field1 10.1.254.0  0.0.0.64
field1 10.1.254.128  0.0.0.63
field1 10.1.158.0  15.255.0.255
field1 10.1.160.0  0.0.0.37
field1 10.1.161.0  0.0.146.255

[download]
And the (truncated) output: 
Checking mask 0.0.0.0
        octets array is 0 0 0 0
        checking octet 0
        checking octet 0
        checking octet 0
        checking octet 0
Mask is 1

Checking mask 0.0.0.64
        octets array is 0 0 0 64
        checking octet 0
        checking octet 0
        checking octet 0
        checking octet 64
                Unequal: oc is 64, flagvalue is 0
Mask is 0

Checking mask 0.0.0.63
        octets array is 0 0 0 63
        checking octet 0
                Unequal: oc is 0, flagvalue is 255
        checking octet 0
                Unequal: oc is 0, flagvalue is 255
        checking octet 0
                Unequal: oc is 0, flagvalue is 255
        checking octet 63
                Unequal: oc is 63, flagvalue is 255
Mask is 0

[download]
Right here: Checking mask 0.0.0.63
octets array is 0 0 0 63
checking octet 0
Unequal: oc is 0, flagvalue is 255

$flagvalue is 255. It should have been initialized to 0 when ValidateMasks() was called, shouldn't it? It appears to be retaining the value from the previous time it was called. Am I overlooking something obvious or do I really not understand Perl initialization and scope?

In reply to Variable initialization / reinitialization by Anonymous Monk

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