Perl/Shell Knowledge Sharing: Capgemini - Perl Interview questions with additional answers

Below are the collection of technical questions asked in the telephonic round and F2F round in Capgemini interview for Production Support.

Brief about data structures in perl.

Scalars, Arrays and Hashes

What are the differences between arrays and lists?

* Lists are constant data while arrays are variables.

* Arrays have a name to identify them, while lists don't.

* Elements of an array can be modified and stored in the same array variable but the same is not possible with lists.

* Stack (push,pop) and queue (unshift,shift) operations are possible only on arrays and not possible on lists.

What are the differences between arrays and hashes?

* Arrays have numerals as indices while hashes have keys (strings) as indices.

* Arrays are often ordered list while hashes are unordered list.

Have you used modules in perl? Can you brief about a module and its functions or sub routines?

1. File::Find

2. File::Copy

3. XML::Simple

4. DBI

5. WWW::Machanize

6. CAM::PDF

7. CGI

8. DBIx::Class

9. Net::FTP

Difference between use and require.

http://stackoverflow.com/questions/1161624/in-perl-what-is-the-difference-between-use-and-require-for-loading-a-module

How to create objects in OO perl?

Write a perl script to validate an IP address.

A partly correct way is given here -- http://perl-interview-questions-answers.blogspot.in/2013/06/lets-see-who-finds-bug-in-this.html

How to sort a numeric array?

http://stackoverflow.com/questions/3574336/how-to-sort-numbers-in-perl

What are the differences between grep and map functions?

http://stackoverflow.com/questions/575490/whats-the-difference-between-grep-and-map-in-perl

How to sort a hash with key,values pairs as name_of_person,age based on their age?

%hash = #hash map of format name => age
(
"ganesh" => "26",
"kumaresh" => "27",
"kannan" => "30",
);
foreach $value (sort {$a <=> $b} values(%hash))
{
print "$value\n"
}

How to remove duplicate entries in an array?

my @arr = (1,2,2,3,4,4,5,5,5,6,6,1,1,1); #array having duplicates
my %hash;
foreach (@arr)
{
$hash{$_} = undef; #creating a hash key for each array element. this line helps in removing duplicates since hash keys cannot be duplicated and new duplicate key overwrites the old key.
}
my @res = keys %hash;
print "@res"; #prints array without puplicates