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Perl: the Markov chain saw

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Perl still surprises me, I found this code example in B::CC

sub skip_on_odd { next NUMBER if $_[0] % 2 } NUMBER: for ($i = 0; $i < 5; $i++) { skip_on_odd($i); print $i; }
produces the output 024

I would never believe that it works because the goto and the label are in different scopes but well...

from goto I can read

... It can be used to go almost anywhere else within the dynamic scope, including out of subroutines,...

So what exactly is a "dynamic scope" here? Does it mean that the label NUMBER is kind of a localized global, which is visible in called subs?

And jumping out of the sub is guarantied to clean the call stack (such avoiding any overflows)?

So please explain why a normal call works, but not the out-commented goto call (which tries to avoid the superfluous call frame)?

sub jump { goto NESTED }; sub cont { for $i (0..3) { for $j ("a".."c") { print "$i,$j\t"; jump(); #1 #goto &jump; #2 } NESTED: } } cont();

OUTPUT1  0,a    1,a    2,a    3,a


Can't find label NESTED at /home/lanx/B/PL/PM/ line 1. 0,a

Cheers Rolf

In reply to cross scope gotos? by LanX

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