The Symbol module doesn't need 'no strict qw(refs)' because it doesn't 'use strict' in the first place. :)

Remember that strict, like most pragmas, is lexically scoped. It only applies to the end of the enclosing block (and a file is a block too).

Setting warnings with -w or $^W, on the other hand, is global. Since this can be problematic, perl5.6.0 added a warnings pragma, which is lexically scoped.