Perl Interview Questions 3

Explain about lists?

A list is a construct that associates data elements together and you can specify a list by enclosing those elements in parenthesis and separating them with commas. They could themselves be arrays, hashes or even other lists. Lists do not have a specific list data type.

Does Perl have reference type?

Yes. Perl can make a scalar or hash type reference by using backslash operator.

For example

$str = "here we go"; # a scalar variable

$strref = $str; # a reference to a scalar

@array = (1..10); # an array

$arrayref = @array; # a reference to an array

Note that the reference itself is a scalar.

How to dereference a reference?

There are a number of ways to dereference a reference.

Using two dollar signs to dereference a scalar.

$original = $$strref;

Using @ sign to dereference an array.

@list = @$arrayref;

Similar for hashes.

What happens when you return a reference to a private variable?

Perl keeps track of your variables, whether dynamic or otherwise, and doesn't free things before you're done using them.

How to turn on Perl warnings? Why is that important?

Perl is very forgiving of strange and sometimes wrong code, which can mean hours spent searching for bugs and weird results. Turning on warnings helps uncover common mistakes and strange places and save a lot of debugging time in the long run. There are various ways of turning on Perl warnings:

For Perl one-liner, use -w option on the command line.

On Unix or Windows, use the -w option in the shebang line (The first # line in the script). Note: Windows Perl interpreter may not require it.

For other systems, choose compiler warnings, or check compiler documentation.

What are scalar data and scalar variables?

Perl has a flexible concept of data types. Scalar means a single thing, like a number or string. So the Java concept of int, float, double and string equals to Perl's scalar in concept and the numbers and strings are exchangeable. Scalar variable is a Perl variable that is used to store scalar data. It uses a dollar sign $ and followed by one or more alphanumeric characters or underscores. It is case sensitive.