Bareword "old" not allowed while "strict subs" in use at ./re line 7.
Bareword "g" not allowed while "strict subs" in use at ./re line 7.

##</code><code>##

$ perl -MO=Deparse re
my $one = 'TestnewTest';
$one =~ s//new/;
'???';
'???';
print "$one\n";
re syntax OK

##</code><code>##

$one =~ s//new/; 'old';; 'g';