Argument isn't numeric - question

Question

Why doesn't the first example output a warning?

#!/usr/bin/env perl
use warnings;
use 5.012;

my $c = "9\n";
say $c * 2;

my $d = "6a";
say $d * 2;

# 18
# Argument "6a" isn't numeric in multiplication (*) at ./perl8.pl line 9.
# 12

Answer 1

When converting a number from a string, trailing whitespace is ignored, and newline counts as whitespace, so a warning isn't generated. Converting "9 " doesn't generate a warning either.