Challenge 3: A Simple Calculator — Possible Solution
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use strict;
use warnings;
use feature 'say';

my $a = 10;
my $b = 5;

say "Sum: " . ($a + $b);
say "Difference: " . ($a - $b);
say "Product: " . ($a * $b);
say "Quotient: " . ($a / $b);

Output:
Sum: 15
Difference: 5
Product: 50
Quotient: 2

WHY THIS WORKS AS AN ANSWER
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$a = 10; and $b = 5; reuse the chapter's own numeric-scalar
declaration pattern, and the four operators (+, -, *, /) are reused
directly from the chapter's own arithmetic examples, applied here to
variables instead of two bare number literals.

Concatenation with . is used here deliberately rather than
interpolation, because $a + $b needs to be evaluated as an
EXPRESSION first — inside a double-quoted string, "$a + $b" would
just interpolate $a and $b separately and print the literal "+"
character between them (e.g. "10 + 5"), not perform the addition.
Wrapping the arithmetic in parentheses and joining it to the label
string with . ensures the calculation happens first, and only the
final numeric RESULT gets joined onto the label.

Each line reuses the same "label" . (expression) shape, applied to a
different operator per line — producing four independently labeled
results in the exact format the challenge requests.