Perl Code

Answer to question 1 #logic we are retrieving the value after the second (.) and third (.) and checking if they are in the range or not # $1 = first value match in the pattern match which is there in first parenthesis (d)+ # $2 = second value match in the pattern match which is there in second parenthesis (d)+

Code
 
/home/gkhurana> perl
 
chomp($ip=<STDIN>);
if($ip =~ m/172.125.(d+).(d+)/)
{
   if ($1 >=1 and $1 <=25 and $2 >=0 and $2 <=255 )
        {
        print "
IP address is within the range
 " ;
        }
        else
        {
        print "
IP address is out of the range
";
        }
}
172.125.1.20
 
IP address is within the range
 
/home/gkhurana>
 

First we are searching for a vowel , if its found we are removing it from the string example if input string $in=hello, then since vowels are present in it , we are removing them so $in=hll (removed all vowels) , now we know there were vowels present in the input now we are making sure that rest string should have atleast 3 non vowel characters

Code
print "Please enter the input(0 to exit) :- ";
chomp($in=<STDIN>);
if ($in=~ s/[aeiou]+//gi and $in=~/[b-df-hj-np-tv-z]{3,}/ig)
{
 print "
It contains a vowel and atleast 3 characters which are not vowels . 
";
}
else
{
print "
It does not meet the requirements
";
}
 

answer to question 3: Validated the general email id that we use but not all validation as suggested on http://en.wikipedia.org/wiki/Email_address

Code
/home/gkhurana> perl
 
@input=(a@gmail.com,a@a.ca,bcfdd.com,abc@a.in,aaaaaaaaaaaaaaaaa@a.,abcasbcscdb@A.com,abc1234@yahoo.com,abc1234abc@yahoo.co.in,1234@yahoo.com,sachin.te@yahoo.com);
foreach $in (@input)
{
# first matching should start with character then . or _ and then numbers and then @ symbol after that yahoo.com or it could be yahoo.co.in
# assuming that atleast 2 character should come after .
 
if ($in=~/^ [a-z]+ .?  \_?   [0-9]*   [a-z]*   @   [a-z]+  .[a-z]{2,} .?([a-z]{2,})?$  /ix)
{
 print "
$in  is a correct email id
";
}
else
{
 print "
$in  is not a correct email id
 ";
}
}
^D
a@gmail.com  is a correct email id
 
a@a.ca  is a correct email id
 
bcfdd.com  is not a correct email id
 
abc@a.in  is a correct email id
 
aaaaaaaaaaaaaaaaa@a.  is not a correct email id
 
abcasbcscdb@A.com  is a correct email id
 
abc1234@yahoo.com  is a correct email id
 
abc1234abc@yahoo.co.in  is a correct email id
 
1234@yahoo.com  is not a correct email id
 
sachin.te@yahoo.com  is a correct email id
 
/home/gkhurana>