How to enhance the operator "+" in perl - perl

Question

Would like to enhance the operator "+" in perl so that it will be regular add operation if both operands are numbers
$a = 11;
$b = 12;
$x = $a + $b; #expect it to be 23
If one operand is a string, then convert all operands as string and treat them as concatenation.
$a = 11;
$b = " cars";
$x = $a + $b; #expect it to be "11 cars"
If this is not possible, wonder if it's possible for me to create a new operator to do it.

Answer 1

Perl makes no distinction between variable types. This is pretty much in line with how shell scripts and awk scripts work. A variable might be a number in one place in your program and a string in another place. Perl hopes that you know what you're doing:
#! /usr/bin/env perl
#
use strict;
use warnings;
use feature qw(say);
my $vendor_id = "344";
my $inventory_item = "23942";
print "You want to order item ";
print $vendor_id + $inventory_item;
print "\n";
This will print:
You want to order item 24286
Which added my $vendor_id to my $inventory_item. What you probably wanted to do was to concatenate them.
You want to order item 34423942
There's no way Perl can tell if you meant a variable to be a string or number, so Perl forces you to use operators. The + is a numeric addition while . is a string concatenation. In many languages, this would be the same operator, but in Perl, we need two distinct operators. To do what you want, you would have done this:
print $vendor_id . $inventory_item;
vs.
print $vendor_id + $inventory_item;
This is why Perl has two completely different sets of boolean operators: One set for numeric comparisons and one for strings. This gives Perl great flexibility because a variable can be treated as a number in one place, then as a string in another. However, it also means you better know what your variable is suppose to represent.
In Python, Java, Swift, and in many other languages, you declare a variable as either a string or a number. Beware if you declare a variable as a string and try to add them, or declare them as some form of numeric data and try to concatenate them. In most languages, you have to cast variables from one form to another using either methods (like int2sting) or a declaration.
If you truly don't know your data, and are not sure what it represents, you can use looks_like_number from Scalar::Util. This isn't a builtin function, but Scalar::Util is a standard module, and is probably already in your Perl distribution:
use strict;
use warnings;
use feature qw(say);
use Scalar::Util qw(looks_like_number);
my $first = "11";
my $second = " of cars";
if ( looks_like_number($first) and looks_like_number($second) ) {
say $first + $second; # Add the two numbers together
}
else {
say $first . $second; # At least one is a string, so concatenate them
}
Now, if both $first and $second look like numbers, they'll be added. However, if one or the other doesn't look like a number, they'll be concatenated.
There are Perl modules (and I can't remember them) that will turn Perl into a declarative language where variables are told they're a string, integer, floating point number, etc. Most of these attempts are incomplete for many reasons. For example, you can't stop someone from using the more ambiguous built in syntax.
If you have more advanced Perl knowledge, you can create your own objects types, and use the overload pragma to overload the operation definition for each class type:
use strict;
use warnings;
use feature qw(say);
use Object::Perl; # Hypothetical module
my $first = Object::Perl::String->new(11);
my $second = Object::Perl::String->new(" cars");
say $first + $second; # Overloaded "+" to concatenate two Object::Perl::String types
$first = Object::Perl::Int->new(11);
$second = Object::Perl::Int->new(12);
say $first + $second; $ Overloaded "+" to add two Object::Perl::Int types
However, if you're going through all that trouble, you might as well learn Python.

Answer 2

That makes no sense. For example, what should the following output?
my $x = 11; print("$x\n");
my $y = 12; print("$y\n");
print($x+$y, "\n");
my $m = "11"; print(0+$m, "\n");
my $n = "12"; print(0+$n, "\n");
print($m+$n, "\n");
Keep in mind that $x and $m are identical (they both contain a number and a string), and so are $y and $n.
SV = PVIV(0x16f2dd8) at 0x16fe8b0 $x
REFCNT = 1
FLAGS = (PADMY,IOK,POK,pIOK,pPOK)
IV = 11
PV = 0x16f7b30 "11"\0
CUR = 2
LEN = 16
SV = PVIV(0x16f2e20) at 0x16fea60 $m
REFCNT = 1
FLAGS = (PADMY,IOK,POK,pIOK,pPOK)
IV = 11
PV = 0x17086b0 "11"\0
CUR = 2
LEN = 16
SV = PVIV(0x16f2df0) at 0x16fe8f8 $y
REFCNT = 1
FLAGS = (PADMY,IOK,POK,pIOK,pPOK)
IV = 12
PV = 0x171eee0 "12"\0
CUR = 2
LEN = 16
SV = PVIV(0x16f2e08) at 0x170eee8 $n
REFCNT = 1
FLAGS = (PADMY,IOK,POK,pIOK,pPOK)
IV = 12
PV = 0x17320e0 "12"\0
CUR = 2
LEN = 16