in reply to Hacking Perl Code

You should have better asked here -> "check modules used by a script and their version" or at least link to the original thread.

What it does is to compile a file's content given as parameter within an eval after prepending a UNITCHECK block which is executed right after compilation and exits right away.

Within this block the required (resp used) modules are parsed from the keys of %INC.

But the author is overly optimistic about parsing code without executing it. It was already mentioned that BEGIN blocks are executed at compile time, additionally does every use execute an import function.

And much more magic ...

Cheers Rolf

( addicted to the Perl Programming Language)

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Re^2: Hacking Perl Code
by Discipulus (Canon) on Apr 09, 2014 at 07:49 UTC
    thanks LanX, as suggested I added a link to this post in the original one.

    I also added an update to the same post to explain better my optimistic sentence parsing code without executing it. Doing this i discovered that my solution executes even less code than the perl -c -d:TraceUse script.pl one.

    HtH
    L*
    There are no rules, there are no thumbs..
    Reinvent the wheel, then learn The Wheel; may be one day you reinvent one of THE WHEELS.
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      > Doing this i discovered that my solution executes even less code than the perl -c -d:TraceUse script.pl one.

      Could you please elaborate what you mean with less code?

      Can you provide an example showing the difference?

      TraceUse hooks into @INC with a callback like recently discussed.

      With this approach its even possible to report before anything is included and to avoid the import.

      Cheers Rolf

      ( addicted to the Perl Programming Language)

[reply]
        Dear LanX,
        i only meant, as explained in the update of the original post that my solution only executes any BEGIN block and no more, while with perl -c -d:TraceUse script.pl all the BEGIN UNITCHECK CHECK blocks are executed.
        I was wrong (so thanks for your question), because my code also executes any END blocks and even other UNITCHECK already present, because those blocks run LIFO.
        Here some code to demonstrate the concept. With a script called test_of_executed_code.pl as follow: 
        BEGIN{print qq(1-begin\n)};
UNITCHECK {print qq(2-unitcheck\n)};
CHECK {print qq(3-check\n)};
INIT {print qq(4-init\n)};
  print qq(5-main\n);
END{print qq(6-end\n)};

        [download]
        You can now compare the two solutions: 
        some_win>perl -c -d:TraceUse test_of_executed_code.pl
1-begin
2-unitcheck
3-check
Modules used from test_of_executed_code.pl:
test_of_executed_code.pl syntax OK

        [download]
        while with my script you'll see: 
        some_win>perl used_modules.pl test_of_executed_code.pl
1-begin
2-unitcheck
strict               1.04
warnings             1.12
6-end

        [download]
        The only way i found to prevent the END blocks to be executed is to change, in the UNITCHECK part of the original script, exit; with an ugly exec qq(perl -e "exit"); that produces: 
        some_win>perl used_modules.pl test_of_executed_code.pl
1-begin
2-unitcheck
strict               1.04
warnings             1.12

        [download]
        But, considering the LIFO aptitude of the UNITCHECK blocks, i can do it better and change eval $begin.$content; with eval $content.$begin; producing: 
        some_win>perl used_modules.pl test_of_executed_code.pl
1-begin
strict               1.04
warnings             1.12

        [download]
        Thanks for the opportunity to learn something more.
        L*

        There are no rules, there are no thumbs..
        Reinvent the wheel, then learn The Wheel; may be one day you reinvent one of THE WHEELS.
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