Minor correction - my is block scoped (or more technically speaking "lexically" scoped) with the largest containing "block" (lexical unit) being the file. Example:

use strict;
use warnings;

package Goo;
my $x=100;
print "package=", __PACKAGE__, " x=$x\n";

package Boo;
{
  my $x=200;
  print "package=", __PACKAGE__, " x=$x\n";
}

package Foo;
print "package=", __PACKAGE__, " x=$x\n";

#outputs
package=Goo x=100
package=Boo x=200
package=Foo x=100
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