I thought I found a bug of Perl

vincentaxhe has asked for the wisdom of the Perl Monks concerning the following question:

test.pl as below;

my $a = "abc";
my @b = $a =~ /.(?!a)/g; #comment this line to see the output
my $c = 'test';
$c =~ s///;
print $c
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run 'perl test.pl'; line 2 run or not, affect the rest. comment it and see for yourself.I use perl 5.38 in manjaro.

ADD:

It's beyong all expectations.