$ perl -MO=Concise,func -E'my $y; { my $x; sub func { my $z; say $x+$y
++$z }}' 
main::func:
9  <1> leavesub[1 ref] K/REFC,1 ->(end)
-     <@> lineseq KP ->9
1        <;> nextstate(main 6 -e:1) v:%,us,fea=15 ->2
2        <0> padsv[$z:6,7] vM/LVINTRO ->3
3        <;> nextstate(main 7 -e:1) v:%,us,fea=15 ->4
8        <@> say sK ->9
4           <0> padrange[$x:FAKE:; $y:FAKE:] /range=2 ->5
7           <2> add[t5] sK/2 ->8
5              <2> add[t4] sK/2 ->6
-                 <0> padsv[$x:FAKE:] s ->-
-                 <0> padsv[$y:FAKE:] s ->5
6              <0> padsv[$z:6,7] s ->7
-e syntax OK

[download]

IIRC: LexPads (Lexical Scratchpads) are kind of a hash-like structure, roughly similar to symbol-tables. Each scope of the sub has a Pad starting with 0 for the inner scope with { '$z' => SCALARREF }. $x is in Pad-1, $y in Pad-2. The Pads are inspected starting with Pad-0 to find the reference. (see PadWalker for more)

So yes there might be some look up overhead involved, but I'd be surprised if the encountered refs weren't cached at first execution.

Cheers Rolf
(addicted to the Perl Programming Language :)
see Wikisyntax for the Monastery

In reply to Re^2: Why is "any" slow in this case? by LanX
in thread Why is "any" slow in this case? by Anonymous Monk

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