Why is "a" x 3 not considered a constant string...?

As I see it, "a" is a const with x signifying a repeat of 3. With that in mind, I went for a walk:

#!/usr/bin/perl

use strict;
use warnings;
use Data::Dumper::Concise;
use B::Concise qw/ walk_output set_style_standard /;

my $walker = B::Concise::compile('-concise', 'newFunc');
walk_output( \*STDOUT );
print Dumper ( $walker->() );
set_style_standard( 'terse' );
print Dumper ( $walker->() );

sub newFunc {
        my $s = 'a x 3';
}
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In other words, 'a' is the constant string, which seems like the right thing to me; however, 'a x 3' is a constant string. Use that instead.