How to interpolate hashes in double quotes under Perl

Just like we can interpolate scalar variables and arrays in double quotes, why can't we interpolate hashes in Perl.

I always had this question until one day I decided to find the solution and understand the reason.

Reason: http://dev.perl.org/perl6/rfc/237.html

Solution (silly): https://github.com/paragkalra/my_scripts/blob/master/perl/hash_interpolation/hash_interpolation.pl

Add Custom Header to scripts using vim

1. Create a template header: cat ~/.vim_header.pl

:insert

#

# $Id: $

#

# Copyright (c) 2011 Parag Kalra

# All rights reserved.

#

## @script

##

## @summary

##

## @description

##

## @usage

##

## @synopsis

##

## @param

##

## @keywords

##

## @status review

##

## @author

##

## @creation-date

##

## @last-modified

##

## @burts

##

## see-also

.

:insert should be present on first line and . should be present on last line

2. Add following lines to ~/.vimrc

autocmd bufnewfile *.pl so ~/.vim_header.pl

autocmd bufnewfile *.pl exe "1," . 30 . "g/@script.*/s//@script " .expand("%")

autocmd bufnewfile *.pl exe "1," . 30 . "g/@creation-date/s//@creation-date " .strftime("%d-%m-%Y")

autocmd Bufwritepre,filewritepre *.pl execute "normal ma"

autocmd Bufwritepre,filewritepre *.pl exe "1," . 30 . "g/last-modified/s/last-modified .*/last-modified " .strftime("%c")

autocmd bufwritepost,filewritepost *.pl execute "normal `a"

3. Now create a new file having .pl extension and see the magic.

Courtesy: http://www.thegeekstuff.com/2008/12/vi-and-vim-autocommand-3-steps-to-add-custom-header-to-your-file/

Locking Hashes - How to Lock Hashes in Perl

One drawback of hashes is that their keys are barewords which offer little typo protection (especially compared to the function and variable name protection offered by the strict pragma). The core module Hash::Util provides mechanisms to restrict the modification of a hash or the keys allowed in the hash.

For examples have a look at my sample scripts here.

How to find if a Perl module is installed on the System

Quick and Dirty way to find if a Perl module is installed on the System:

perl -MModule_Name -e 1

How to break from if - else in Perl

One of the ways to break from if - else in Perl is to use goto

if ($num =~ /^\d+$/){
if($num == 13){
goto ENDOFIF;
}
} else {
print "Number not found.\n";
ENDOFIF:
}

So if the number is 13 then it will break from the if and place the control right at the end of outer if.

How to calculate the time of execution of a Perl script

Just add the following line any where in your Perl script and it will print its time of execution right at the end:

# This calculates the time of execution of the Perl script.
END {warn "\nTime of execution - ", time - $^T, " second(s)\n"}

Connecting to MySQL Database through PERL

FAQ: How to connect to MySQL database through PERL.


SOLUTION:
1. Install MySQL database. MySQL community server comes free of cost and is distributed under GNU General Public License.

2. I would instead recommend installing a package called WAMP server which provides MySQL community server, Apache server and PHP. It also provides many effective tools like PHPMyAdmin which can be used for database administration. Also WAMP server comes free of cost and is distributed under GNU General Public License.

3. To check if the MySQL server is running, execute:
telnet 3306
E.G: # telnet 127.0.0.1 3306

4. I would also recommend you to also install SQLYog. It is a very light and effective tool to monitor and manage MySQL database. Again it also comes free of cost and is distributed under GNU General Public License.

5. Create a database in MySQL, a non-root user and give it a password.

6. Install ‘DBI’ perl module through ‘PPM’

7. Install ‘DBD::Mysqlpp” perl module through ‘PPM’

8. You are all set to connect to MySQL database. While connecting make sure that database is already created and you are connecting through a valid user and with correct credentials. To see a sample script execute following on command prompt:
# perldoc DBD::Mysqlpp


REFERENCES:
1. http://dbi.perl.org/
2. # perldoc DBD::Mysqlpp


AUTHOR: Parag Kalra
Email-ID: paragkalra@gmail.com