Re^3: Tiny Perl puzzle

I think B::Deparse gets it wrong -- as it sometimes does -- when you add -p:

My theory: When Deparse tries to add parens wherever it can, it treats the first two as a function call (which was my first guess too). But as tobyink correctly surmised, that first two is treated by print as a filehandle.

This is confirmed by the more low-level output of B::Concise:

$ perl -MO=Concise,-exec, -e 'print ( two + two == five ? "true" : "fa
+lse" )'
1  <0> enter 
2  <;> nextstate(main 1 -e:1) v:{
3  <0> pushmark s
4  <$> gv(*two) s
5  <1> rv2gv sKR/1
6  <$> const(PV "two") s/BARE
7  <$> const(PV "five") s/BARE
8  <2> eq sK/2
9  <|> cond_expr(other->a) lK/1
a      <$> const(PV "true") s
           goto b
d  <$> const(PV "false") s
b  <@> print vKS
c  <@> leave[1 ref] vKP/REFC
-e syntax OK
[download]

It's easy to see from this output that the first two is treated as a typeglob; a filehandle. The second two and the five are treated as barewords; constants in this case, which are then compared to one another. They evaluate to the same constant defined value, which is probably an empty string, equating to 0 for the purpose of numeric equality. So "true" will result, but it's printed to a filehandle that hasn't been attached to anything.

Dave

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Re^4: Tiny Perl puzzle by Anonymous Monk on Jun 07, 2014 at 07:25 UTC
Look at the way Deparse uses whitespace, its subtle <Reveal this spoiler or all in this thread>	[reply] [d/l] [select]
Re^4: Tiny Perl puzzle by LanX (Saint) on Jun 07, 2014 at 15:38 UTC
I don't think so. did you recompile the output? <Reveal this spoiler or all in this thread> Cheers Rolf (addicted to the Perl Programming Language)	[reply]
Re^5: Tiny Perl puzzle by Anonymous Monk on Jun 08, 2014 at 09:17 UTC
I can't test ATM You gotta stop saying that :) Contrary to AnoMonk I doubt space matters. Sure it does, it matters how Deparse places the space, because it matters to perl <Reveal this spoiler or all in this thread> That is exactly as deparsed with -p, behaves exactly like the original	[reply] [d/l]
Re^6: Tiny Perl puzzle by LanX (Saint) on Jun 08, 2014 at 13:33 UTC
> Sure it does, it matters how Deparse places the space, because it matters to perl it depends! ;-) <Reveal this spoiler or all spoilers in this node or all in this thread> update ALSO: <Reveal this spoiler> BUT: <Reveal this spoiler> Cheers Rolf (addicted to the Perl Programming Language)	[reply] [d/l] [select]

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