>perl -wMstrict -le
"my $scalar = 99;
 foo();
 my $scalar = 42;
 sub foo { print qq{scalar in foo: $scalar} }
"
"my" variable $scalar masks earlier declaration in same scope at ...
Use of uninitialized value in concatenation (.) or string at ...
scalar in foo:

>perl -wMstrict -le
"my $scalar = 99;
 foo();
 BEGIN {
   my $scalar = 42;
   sub foo { print qq{scalar in foo: $scalar} }
   }
"
scalar in foo: 42