Question

Regarding Perl, how can references be used in subroutines? Use code examples to support your reasoning.

Answer 1

Please find the following code for pass by references in perl.

Step 1: Declare two list variables @grade = ("one", "two", "three") and @grad1e = ("four", "five")

Step 2: Define function that handles two arguments and it will update the first variable by using the second argument "grade1".

Step 3: In the subroutine have additional variable "append" to be updated with the values from 2nd argument "grade1"

Step 4: Using for loop, iterate the "append" list and store it in "grade" variable which is a first argument.

Program:

USER>cat perlbyRef.pl

#!/usr/bin/perl

my(@grade) = ("one","two","three");
my(@grade1) = ("four","five");
print "Initial: @grade ";

&routineByReference(@grade, @grade1);

print "Updated grade via pass by reference : @grade ";

# This sub routine is used to update the grade variable via pass by reference
sub routineByReference
{
#copy the grade1 to append list variable because sub routines in perl accept only scalar variables
   my(@append) = @{$_[1]};

   my($temp);

#using a temp variable to traverse all the values from append list variable to grade variable.
#Eventually grade variable gets updated in this

   foreach $temp (@append)
   {
#push each value to argument 1, which is grade variable passed as reference
      push(@{$_[0]}, $temp);
   }
}

USER> perl perlbyRef.pl
Initial: one two three
Updated grade via pass by reference : one two three four five