Pragmas (such as use strict), my variables, our declerations (but not package variables), package statements, etc all have lexical scope. A lexical scope spans (includes) its child lexical scope.

use strict;

sub f {
   # strict still in effect in this child block

   if (...) {
      # strict still in effect in this child block

      for (...) {
         # strict still in effect in this child block

         {
            # strict still in effect in this child block
         }
      }
   }
}
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my $n;

sub f {
   # $n is still accessible in this child block

   if (...) {
      # $n is still accessible in this child block

      for (...) {
         # $n is still accessible in this child block

         {
            # $n is still accessible in this child block
         }
      }
   }
}
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{
   use strict;
   # strict still in effect
}
# strict no longer in effect
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{
   my $n;
   # $n accessible.
}
# $n no longer accessible.
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