perl template boilerplate preamble

perl-template.pl

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#                     BEGIN MODERN PERL BOILERPLATE                         #
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# Use perl v5.16.3
# (We're tracking RHEL7 as our baseline)
# Note:
# - `use v5.12` or higher implies `use strict`
#   https://stackoverflow.com/q/6050031
#   https://perldoc.perl.org/feature
#   https://perldoc.perl.org/perl5120delta#Implicit-strictures
#   Note: Standard Preamble redundantly does `use strict` anyway
#   https://www.perl.com/pub/2012/04/perlunicook-standard-preamble.html/
# - But `use v5.12` doesn't imply `use warnings` --- that's not until v5.35
#   https://perldoc.perl.org/functions/use#use-VERSION
#   https://perldoc.perl.org/warnings
# - The matching feature bundle is loaded
#   https://perldoc.perl.org/perlfunc#use-VERSION
#   https://perldoc.perl.org/feature#FEATURE-BUNDLES
#   https://stackoverflow.com/q/1878108
# - The 'v' is required if less than three components
#   For example, this won't work: use 5.16
#   But this will work: use 5.16.0
# - Otherwise, the 'v' is optional
# - Use of the 'v' is the only way in raku née perl 6
#   https://docs.raku.org/language/pragmas
#   https://gist.github.com/robin-a-meade/129bd1f6ed30f19d7ccb3e579beb5ec1
# - Thus it makes sense to use 'v' in the version spec. It is the modern way.
use v5.16.3;

# "All warnings are enabled automatically within the scope of a use v5.35 (or higher) declaration."
# - https://perldoc.perl.org/warnings
# - https://perldoc.perl.org/functions/use#use-VERSION
# In the mean time, we enable all warning in the top level scope here:
use warnings;

use utf8; # Let literals and identifiers in this source code be in UTF-8

# Do the equivalent of -CD for the current lexical scope
#use open IN  => ':encoding(UTF-8)';
#use open OUT => ':encoding(UTF-8)';
# More compactly:
#use open IO  => ':encoding(UTF-8)';
# More compactly:
#use open ':utf8';

# Do the equivalent of -CSD for the current lexical scope
# (It should be noted that STDOUT, STDOUT, and STDERR are global, beyond the current lexical scope)
#binmode STDIN,  ':utf8';
#binmode STDOUT, ':utf8';
#binmode STDERR, ':utf8';
#use open IN  => ':utf8';
#use open OUT => ':utf8';
# More compactly:
use open qw(:std :utf8);

# If you like, use fat comma operator, or qw(). These are equivalent:
#binmode STDOUT, ':utf8';
#binmode 'STDOUT', ':utf8';
#binmode STDOUT => ':utf8';
#binmode qw(STDOUT :utf8);

# To be more strict about valid code points and UTF-8 encoding,
# change :utf8 to :encoding(UTF-8)
# https://stackoverflow.com/q/14566460
# https://perldoc.perl.org/Encode#UTF-8-vs.-utf8-vs.-UTF8

# Or "fatalize" utf8 encoding warnings
# https://www.perl.com/pub/2012/04/perlunicook-standard-preamble.html/
use warnings  qw(FATAL utf8);    # fatalize encoding warnings
# You may relax some utf8 encoding warnings by disabling these sub warnings:
#no warnings "nonchar";      # The 66 forbidden non-characters
#no warnings "surrogate";    # UTF-16 surrogate code points
#no warnings "non_unicode";  # Codepoints over 0x10_FFFF
# https://perldoc.perl.org/perlunicook#%E2%84%9E-2:-Fine-tuning-Unicode-warnings 

# Should we always be strict about UTF-8?
# Sometimes it is convenient, or necessary, to not be.
# For example, when using an invalid code point as a sentinel delimiter.
# http://www.unicode.org/faq/private_use.html
# Todo: Examine how the above approaches behave in the presence of
# sentinels.

# Decode program arguments as UTF-8 (equivalent to the 'A' option letter to the -C flag)
# https://www.perl.com/pub/2012/04/perlunicookbook-decode-argv-as-utf8.html/
use Encode qw(decode_utf8);
@ARGV = map { decode_utf8($_, 1) } @ARGV;

# At this point we have the equivalent of -CSDA.

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#                      END MODERN PERL BOILERPLATE                          #
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say "Hi";

say "[$_]" foreach @ARGV;


# $foo; # This causes an error due to the implicit 'use strict'