Lexically scoped variables are separate from package variables, including those in the default package of main.

$x = 2;
my $x = 3;
print $main::x, ' ', $x, "\n";
$main::x = 4;
print $main::x, ' ', $x, "\n";
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produces:

2 3
4 3

See MJD's Coping with Scoping