What's the reason behind this stuff?

#! perl -s
use 5.010;
use strict;
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"-s" adds some command-line parsing you're not using, and "use 5.010" breaks backward compatibility and (maybe?) enables some features you're not using. IIRC, the standard ritual chant around these parts is

#!/usr/bin/env perl

use strict;
use warnings;
use diagnostics;
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The particularly devout may use

#!/usr/bin/env perl

use Modern::Perl;
use Moose;
use diagnostics;
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The purpose of the repetition is to get people to write things without understanding them, so making up your own chant is confusing and counterproductive.