in reply to How does strict work?
If it helps, I am willing to treat it as black magic and hope that the phase of the moon is right... :-)
UPDATE
What I suspect (verifying it would take some
research) is happening is that $^H is a global variable
which the parser is auto-localizing as it goes through
blocks. So within strict you write to the global, but
within the parser the effect of that modification is
scoped to just the current block. Therefore the part of
the user code that is affected is apparently lexically
scoped.
A couple of other pieces of magic though. First of all when you see an eval, Perl remembers what the correct value of $^H needs to be when it is called. Secondly within a file it needs to essentially do local $^H = $^H; while when it goes out and compiles another file it would have to do local $^H = 0;.
So the magic isn't all that magic, it just looks mysterious because of when it is happening. If you want to test this explanation, each of the following tests another aspect of its behaviour:
(People on windows may need to switch quotes.)perl -e 'print $^H' perl -e 'use strict; print $^H' perl -e 'use strict; no strict; print $^H' perl -e 'use strict; {no strict; print $^H}' perl -e 'use strict; BEGIN {no strict; print $^H}' perl -e 'use strict; {no strict; BEGIN{ print $^H}}'
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