How to pass entire subroutine into hashtable data using perl?

Question

I have the following subroutine which i should pass the routine as hashtable and that hashtable should be again called inside another subroutine using perl?

input file(from linux command bdata):

NAME     PEND RUN SUSP JLIM JLIMR   RATE   HAPPY
achandra 0    48  0    2000 50:2000 151217 100%
agutta   1    5   0    100  50:100  16561  83%

My subroutine:

sub g_usrs_data()
{
    my($lines) = @_;    
    my $header_found = 0;
    my @headers = ();
    my $row_count = 0;
    my %table_data = ();
    my %row_data = ();

    $lines=`bdata`; 
    #print $lines;
    foreach (split("\n",$lines)) {
        if (/NAME\s*PEND/) {
            $header_found = 1;  
            @headers =split;
        }
        elsif (/^\s*$/) 
            {
                $header_found=0;
            }
            $row_data{$row_count++} = $_;
            #print $_;
        }

My query:

How can i pass my subroutine as hash into another subroutine?

example: g_usrs_data() -> this is my subroutine .

the above subroutine should be passed into another subroutine (i.e into usrs_hash as hash table)

example: create_db(usrs_hash,$sql1m)

Answer 1

Subroutines can be passed around as code references. See perlreftut and perlsub.

An example with an anonymous subroutine

use warnings;
use strict;

my $rc = sub { 
    my @args = @_; 
    print "\tIn coderef. Got: |@_|\n"; 
    return 7;  
};             # note the semicolon!

sub use_rc {
    my ($coderef, @other_args) = @_; 
    my $ret = $coderef->('arguments', 'to', 'pass');
    return $ret;
}

my $res = use_rc($rc);
print "$res\n";

This silly program prints

        In coderef. Got: |arguments to pass|
7

Notes on code references

• The anonymous subroutine is assigned to a scalar $rc, making that a code reference

• With an existing (named) sub, say func, a code reference is made by my $rc = \&func;

• This $rc is a normal scalar variable, that can be passed to subroutines like any other

• The sub is then called by $rc->(); where in parenthesis we can pass it arguments

Note that the syntax for creating and using them are just like for other data types

• As anonymous assign by = sub { }, much like = [ ] (arrayref) and = { } (hashref)

• For a named sub use & instead of a sigil, so \& for sub vs. \@ (array) and \% (hash)

• They are used by ->(), much like ->[] (arrayref) and ->{} (hashref)

For references in general see perlreftut. Subroutines are covered in depth in perlsub.

---

See for example this post on anonymous subs, with a number of answers.

For far more see this article from Mastering Perl and this article from The Effective Perler.