$ perl -le" $_ = q\e\; s OeOEO; print "
E

$ perl -MO=Deparse -le" $_ = q\e\; s OeOEO; print "
BEGIN { $/ = "\n"; $\ = "\n"; }
$_ = 'e';
s/e/E/;
print $_;
-e syntax OK

$ perl -le" $_ = q 1e1; s 1e1E1; print "
E

$ perl -MO=Deparse -le" $_ = q 1e1; s 1e1E1; print "
BEGIN { $/ = "\n"; $\ = "\n"; }
$_ = 'e';
s/e/E/;
print $_;
-e syntax OK