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I will finally admit :) that whilst I think I know the When and the Where, I haven't a clue as to the Why!

P:\test>perl -MO=Concise -e"sub f{}; goto +f" b <@> leave[t1] vKP/REFC ->(end) 3 <0> enter ->4 4 <;> nextstate(main 2 -e:1) v ->5 a <1> goto vKS/1 ->b 9 <1> refgen sK/1 ->a ## <<<HERE. - <1> ex-list lKRM ->9 5 <0> pushmark sRM ->6 8 <1> entersub[t2] lKRMS/NO(),TARG,INARGS,1 ->9 - <1> ex-list lK ->8 6 <0> pushmark s ->7 - <1> ex-rv2cv sK/129 ->- 7 <#> gv s ->8 -e syntax OK

Even wading through pp_goto, I couldn't quite work out why it only happens if the function is called in a list context, or indeed why it takes a reference at all. Gut feel tells me its something to do with the fact that the code tries for the goto SUB; variation prior to the goto -LABEL and goto -EXPR variations, and that something is being stacked and not cleaned up, but that's about as far as I got before my brain went into overload.

One good thing came out of it. I now have a much better appreciation of why goto \&func is so gaddamn slow. All that chundering around unwinding stack frames, validating the target isn't a prohibited one etc. I never imagined. I'd always invisioned a simple longjump().

Examine what is said, not who speaks.
"Efficiency is intelligent laziness." -David Dunham
"Think for yourself!" - Abigail

In reply to Re: Re[4]: How's your Perl? by BrowserUk
in thread How's your Perl? by xmath

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