Hi, i need help with below implementation of passing function by reference. I am passing add function to multiply function. It executes first time correctly, but fails next time executing function passed by reference. I have played with code and not able to figure out what i am missing. Below is my code. 

use strict;
use warnings;


our $static_counter = 1;

sub add{
    
    my ($x, $y) = @_;
    my $sum = $x + $y;
    print "Sum within function: $sum\n";    
    return ($sum);
}

sub counter {
    my $cnt = $static_counter++;
    print "Value of count in subroutine  $cnt\n";
    return($cnt);
}

sub multiply{
    my ($x, $y, $add_ref, $counter_ref) = @_;
    
    my $cnt_in;
    my $add_in;
    my $mul = 1;
    

    
    $mul = ($x * $y * $$add_ref * $counter_ref->());
    print "Multi : $mul\n";    
    
    $add_in = $add_ref->(20,5);  ### Getting Error Here 
    ###  Not a Code Reference
    $mul = ($x * $y * $add_in * $counter_ref->()); 
    print "Multi : $mul\n";         
    
    return $mul;
    
}

sub a {    
    my $z; 
    
    $z =  multiply(4,5, \&add(10,1), \&counter);
    $z =  multiply(4,5, \&add(10,1), \&counter);
}

a();

[download]

In reply to Not Coder reference error - when i pass function by Refernce by pks283

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.