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(Answers) Re: Barstool Trivia

by dchetlin (Friar)
on Dec 25, 2000 at 06:05 UTC ( #48220=note: print w/replies, xml ) Need Help??

in reply to Re: Barstool Trivia
in thread Barstool Trivia

Oops, sorry about that. I'd given the answer in a /msg and totally forgotten that I hadn't given it in a node.

Recall that this is a fairly ambiguous question, and that my answer really just reveals what the source considers to be different scopes.

That answer is found in cop.h, line 360 as of recent perls.

#define CXt_NULL 0 #define CXt_SUB 1 #define CXt_EVAL 2 #define CXt_LOOP 3 #define CXt_SUBST 4 #define CXt_BLOCK 5 #define CXt_FORMAT 6

OK, the easy ones first

  • CXt_LOOP is for, e.g., while (<>) { ... }.
  • CXt_BLOCK is for regular old blocks, like do { ... } while <>.
  • CXt_EVAL is for eval STRING, not eval BLOCK, which is covered by CXt_BLOCK.
  • CXt_SUB is for a subroutine.

That leaves three: CXt_NULL, CXt_SUBST, and CXt_FORMAT. You can probably guess what CXt_SUBST and CXt_FORMAT do, even though the fact that they start new scopes may be surprising.

[~] $ perl -le'$_="foo";s/foo/my $x="bar"/e;print;print ">>>$x<<<"' bar >>><<<

There's s/// creating a new scope. Here's format:

[~] $ cat tmp/format format = @<<<<<<< my $x = "foo" . write; print ">>>$x<<<"; [~] $ perl -l !$ perl -l tmp/format foo >>><<<

OK, so what does that leave us with? CXt_NULL. CXt_NULL is the block passed to `sort', strangely enough. It's also referred to as a pseudo-block throughout the source.


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