On Compilation, Call Trigger Policy: Now vs Inline

ian has asked for the wisdom of the Perl Monks concerning the following question:

While reading The Camel, ch18 Table 18-1 on page 484 (3rd edition), I came across this notion of "Call trigger Policy".

I'm confused about the difference between "Inline", and "Now".

I see that "Now" applies to BEGIN blocks, and this seems straightforward. But then eval introduces "Inline", and "Call later". I believe I saw someone earlier tonight give some example with print and sub's evaluating their arguments; I believe this means "jumping back" from runtime into compile time.

-- Ian Tegebo

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Re: On Compilation, Call Trigger Policy: Now vs Inline by sh1tn (Priest) on Dec 06, 2007 at 13:45 UTC
It is written:If you think of an eval STRING as a call back from the interpreter to the compiler, then you might think of a BEGIN as a call forward from the compiler into the interpreter. Both temporarily put the current activity on hold and switch modes of operation. Pretty self-explanatory. `print "start main running here\n"; eval "BEGIN{print qq(BEGIN: before eval compilation at run-time +\n)} END{print qq(END: from eval STRING\n)}"; eval {BEGIN{print qq(BEGIN: before eval compilation at compile-t +ime\n)} END{print qq(END: from eval BLOCK\n)}}; END { print "END: done running\n" } BEGIN { print "BEGIN: still compiling\n" }` [download]	[reply] [d/l]
Re^2: On Compilation, Call Trigger Policy: Now vs Inline by ian (Beadle) on Dec 06, 2007 at 17:26 UTC
I'm in agreement about the straightforwardness of call back and call forward with respect to interpreter->compiler and compiler->interpreter; it's the difference between the call trigger policy of "Now" vs "Inline" that's confusing to me. Is it merely that BEGIN is always triggered at the beginning of the line versus an `eval` which can be triggered anywhere within one? -- Ian Tegebo	[reply] [d/l]
Re: On Compilation, Call Trigger Policy: Now vs Inline by Anonymous Monk on Dec 06, 2007 at 11:08 UTC
Most monks don't have that book	[reply]
Re^2: On Compilation, Call Trigger Policy: Now vs Inline by Erez (Priest) on Dec 06, 2007 at 12:14 UTC
Most monks don't have that book Most monks don't have Programming Perl? I'd say other wise, most monks do have it. I don't read passages from it every night before I go to sleep, but I have a copy at my work desk. It's the second best thing to a canonical text in the Perl community. `Software speaks in tongues of man; I debug, therefore I code.`	[reply] [d/l]