Compile time problem

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

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Re: Compile time problem by FunkyMonk (Bishop) on Oct 06, 2007 at 15:13 UTC
String eval compiles at runtime and will avoid the error in older perls (you'll have to move the declaration of `$mem` to avoid a scoping issue). `my $var = ''; my $mem; if($] > 5.007) { if( eval q{open ($mem, '>', \$var) } ) {print "Success\n"} } else {print "Ok\n"}` [download]	[reply] [d/l] [select]
Re^2: Compile time problem by syphilis (Archbishop) on Oct 06, 2007 at 15:31 UTC
Thanks, FunkyMonk ... that looks like the "Aaaah, I see" moment I was after. Does that "q{}" stuff work ok on 5.00505 ? (I don't actually have a 5.00505 to test with ... though I may yet build one.) Cheers, Rob	[reply]
Re^3: Compile time problem by FunkyMonk (Bishop) on Oct 06, 2007 at 16:09 UTC
Good point. I don't know when `q{}` (etc) made their first appearance in perl. Just use appropriate quoting and escaping if it doesn't work, but I'm sure some Monk will appear with the answer before too long.	[reply] [d/l] [select]
Re^4: Compile time problem by shmem (Chancellor) on Oct 06, 2007 at 20:58 UTC
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Re: Compile time problem by BrowserUk (Patriarch) on Oct 06, 2007 at 16:56 UTC
It's before my time, but didn't IO::String work with 5.005? Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. "Science is about questioning the status quo. Questioning authority". In the absence of evidence, opinion is indistinguishable from prejudice. "Too many [] have been sedated by an oppressive environment of political correctness and risk aversion."	[reply]
Re: Compile time problem by perlfan (Parson) on Oct 06, 2007 at 15:13 UTC
Doesn't the first argument of `open` have to be a file handle, i.e, bare word (no sigil or `my`)? Or does your problem have to do with evaluating `$]`?	[reply] [d/l] [select]
Re^2: Compile time problem by FunkyMonk (Bishop) on Oct 06, 2007 at 15:24 UTC
See open. The 3 argument open first appeared in perl 5.6 (first appearance in a production perl, anyway)	[reply] [d/l] [select]
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Re: Compile time problem by ikegami (Patriarch) on Oct 08, 2007 at 07:39 UTC
One solution is to move the problem code into a module and include the module conditionally.	[reply]
Re: Compile time problem by graff (Chancellor) on Oct 06, 2007 at 16:07 UTC
I'm sorry, but I don't quite understand what your real goal is here. Do you intend to open the output file only if the perl version is > 5.007, otherwise don't open the output file? If so, I'm not sure that the benefit of using a lexically scoped file handle is worth the hassle if the code still has to run on older perl versions. Do you have some compelling reason for needing to use a lexically scoped file handle? OTOH, if the goal is "open the file this way if perl is > 5.007 and open it the old way otherwise", that would be a really bad idea, because then you'd have to check the version and use eval every time you write to the file handle. Don't do that. UPDATE: Apologies again... I just noticed this bit: (Changing the open call to a 2 argument form is not a viable solution :-) This seems to answer my first question -- no way you would want to open the file if running under an older version (which does not support 3-arg open). Perhaps you could elaborate on why a 2-arg open is not viable, and how that relates to the need to run under older versions of perl. last update: D'oh!! why didn't I notice "\$var" the first time?! Still, I'm curious why you would add this in a script that is supposed to run under older versions...	[reply]
Re^2: Compile time problem by syphilis (Archbishop) on Oct 07, 2007 at 10:38 UTC
I'm curious why you would add this in a script that is supposed to run under older versions It's all to do with the FileHandle::Fmode test suite. The module should work ok with perl 5.00505, but offers additional features for later builds of perl. The test suite needs to test the additional features on recent builds of perl - but to not test those features on ancient builds of perl (where such tests break perl). Cheers, Rob	[reply]
Re: Compile time problem by Anonymous Monk on Oct 06, 2007 at 20:53 UTC
`my $mem; my @stuff = \$mem, '>', \$var; open @stuff ..` [download]	[reply] [d/l]