a) are the -s and -l switches necessary?

They are in every script I write, unless the function of the script requires their removal to operate properly; which is a very rare occurrence.

1. The -l so I don't have to litter my code with  . "\n"; or equivalent.
2. The -s so that if I want to add some simple parameterisations. Eg.

   #! perl -slw
   use strict;
   use Benchmark qw[ cmpthese ];
   
   sub f1 { # ( [$:arg] )
       use 5.007003; # perl v5.7.3; required for List::Util to be availab
   +le in CORE
       use List::Util qw/ first /;
       my $arg = first { defined && length } ( shift, 'default_value' );
       $arg;
   }
   
   sub f2 {
       my $arg = defined $_[0] && length $_[0] ? shift : 'default';
       $arg;
   }
   
   our $ITERS //= 1000;
   our @args = ( undef, '', 'fred', 1, 1.5 ) x $ITERS;
   
   cmpthese -1, {
       stupid => q[ f1( $_ ) for @args ],
       simple => q[ f2( $_ ) for @args ],
   }
   
   __END__
   C:\test>junk0 -ITERS=10000
            Rate stupid simple
   stupid 12.8/s     --   -58%
   simple 30.2/s   136%     --
   [download]