Dear Monks,

Thanks you for the exicting read. As promised, I did my homework and tried to comment the code you provided.

Please find my endeavours below.

Looking forward to your replies and comments, I am sure I lack some basic understanding and proper perl terminology

Thanks a mil in advance for your support.

#!/usr/bin/perl --
use strict;
use warnings;
use Data::Dump qw/ dd /;
# Creates a shortcut for calling Data::Dumper, writing dd is enough to
+ call module
Main( @ARGV );
# main function, takes every file (as an argument) that is passed to @
+ARGV, might be command line or files
#that are read in
exit( 0 );
#not really a clue, maybe main exits if no arguments are passed to it

#This defines the subrotine Main which is called in line 6 (in my edit
+or at least)
sub Main {
    dd( -argv, \@ARGV );
#calls Data::Dumper via reference => possibly to print which files are
+ being passed as arguments (control function) 
    for my $ar ( @ARGV ){
            #a for loop to treat each file that has been passed as arg
+ument to @ARGV with the sub Sky
            # each individual file assigned to $ar is in turn passed a
+s a parameter to the subroutine
       Sky( $ar );
    }
    Sky(6);
#not really a clue => Does that mean that the sub stops after six runs
+ 
}

#defining subroutine Sky
sub Sky {
    my( $ra ) = @_;
    # variable for the argument(s) passed to the sub, @_ accepts every
+ argument passed to sub, i.e. the files passed to main
    dd( -ra, $ra );
    #print data strucutre of the files -parameter -ra
    dd( -args, \@_ );
    #print data strucutre of the arguments passed to the subroutine
}


__END__
$ perl sky
("-argv", [])
("-ra", 6)
("-args", [6])

# explains what sky does
$ perl sky a b c
#if I were to pass a, b, c
("-argv", ["a", "b", "c"])
#@ARGV would contain ["a", "b", "c"]

#Lists individual files as they are passed to both the sub Sky and sub
+ Main
("-ra", "a")
("-args", ["a"])
("-ra", "b")
("-args", ["b"])
("-ra", "c")
("-args", ["c"])

#Still no clue about the number, sorrry
("-ra", 6)
("-args", [6])
[download]

Hello PitifulProgrammer,

Here’s some feedback on your annotations:

use Data::Dump qw/ dd /;
# Creates a shortcut for calling Data::Dumper, writing dd is enough to
+ call module
[download]

Say rather, writing dd is now enough to call Data::Dump::dd. But actually qw/ dd / is not needed here, because the Data::Dump module exports dd by default.

Main( @ARGV );
# main function, takes every file (as an argument) that is passed to @
+ARGV, might be command line or files
#that are read in
[download]

Correct, but note that in Perl, unlike in C, you don’t need a main function. (I assume that by “command line” you mean command line options.)

exit( 0 );
#not really a clue, maybe main exits if no arguments are passed to it
[download]

No, exit terminates the script and returns its argument to the shell. By convention, an exit value of zero means “success: the script terminated without errors.”

    dd( -argv, \@ARGV );
#calls Data::Dumper via reference => possibly to print which files are
+ being passed as arguments (control function)
[download]

No, dd is a Data::Dump function; Data::Dumper is a different module.

    Sky(6);
#not really a clue => Does that mean that the sub stops after six runs
[download]

No, it’s just another call to sub Sky with the literal 6 passed as an argument instead of the variable $ar.

    my( $ra ) = @_;
    # variable for the argument(s) passed to the sub, @_ accepts every
+ argument passed to sub, i.e. the files passed to main
[download]

Yes, but note that only the first of these arguments is being copied to the scalar variable $ra. (All the arguments passed to the sub remain in the array @_.)

Hope that helps,

Athanasius <°(((>< contra mundum

Iustus alius egestas vitae, eros Piratica,

But actually qw/ dd / is not needed here, because the Data::Dump module exports dd by default.

While technically its "not needed", it sure does document rather well where dd comes from :) so its there for documentation

Dear Athanasius,

Thank you for going through my comments and providing feedback. I am quite happy that I was not completely wrong about all lines.

However some questions remain:

Why was the subroutine called with 6 passed as an argument. Was this just for demonstrating that not only strings but also numbers can be passed to a sub?.

Could you please clarify why only the first argument $ra is passed an the others remain in the array? Does that mean that arguments to a sub are passed in some kind of for loop?

my( $ra ) = @_;
    # variable for the argument(s) passed to the sub, @_ accepts every
+ argument passed to sub, i.e. the files passed to main
[download]

Looking forward to your feedback. Will work on the inital code and try to use more subroutines.

Thanks a mil for your support

Kind regards

C.