use diagnostics; # they're very very good

perl_assignment_error.pl

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

=pod

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This gist is all about the `use` statemtents above

I worked in perl for more than a year without knowing 
perl had this kind of descriptive error output

I had a hunch one day after I had seen this error;
specifically that using a stricter standard would
have had to point out an incorrect assignment.

The company I worked for at the time _only_ required 
`use strict;` and I had seen use of `use warnings;`
only in standalone code because the amount of
errors that would spill out of internally 
developed libraries was insane.

I turned on `use diagnostics` for the first time
and when you run this code with that strict of a 
standard, Perl stops you and explains with an essay
longer than this one why what you did is technically
incoherent.

use this code by typing 

perl ./perl_assignment_error.pl;

in any linux distribution after downloading or copying
this file

=cut

#-----------------------------------------------------
# The actual code
#-----------------------------------------------------

my $string = "Hello World";
# regex matching the first letters with groups, 
#	so $1 should be 'Hello'
#	   $2 should be 'World'
$string =~ /(H.*)\s(W.*)/;

# this is where it hits the error in #use warnings or #use diagnostics
my ($h, $w) = $1, $2;
# the correct use of this functionality I wanted is 
# my ($h, $w) = ($1, $2); # parentheses are very important

# prints out 'h: Hello, w: ' and a newline because of the assignment error
print STDOUT "h: $h, w: $w\n";
exit;