Question

I googled about #!/usr/bin/perl, but I could not find any satisfactory answer. I know it’s a pretty basic thing, but still, could explain me what is the significance of #!/usr/bin/perl in Perl? Moreover, what does -w or -T signify in #!/usr/bin/perl? I am a newbie to Perl, so please be patient.

Answer 1

The #! is commonly called a “shebang” and it tells the computer how to run a script. You’ll also see lots of shell-scripts with #!/bin/sh or #!/bin/bash.

So, /usr/bin/perl is your Perl interpreter and it is run and given the file to execute.

The rest of the line are options for Perl. The “-T” is tainting (it means input is marked as “not trusted” until you check it’s format). The “-w” turns warnings on.

You can find out more by running perldoc perlrun (perldoc is Perl’s documentation reader, might be installed, might be in its own package).

For scripts you write I would recommend starting them with:

#!/usr/bin/perl
use warnings;
use strict;

This turns on lots of warnings and extra checks – especially useful while you are learning (I’m still learning and I’ve been using Perl for more than 10 years now).