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Re: How does next label work?

by moritz (Cardinal)
on Jan 06, 2013 at 10:04 UTC ( #1011869=note: print w/replies, xml ) Need Help??

in reply to How does next label work?

I thought next is just another way to say goto

Well, it's not. You can see that next and goto compile to different ops internally:

$ perl -MO=Concise -e 'X: next X' 4 <@> leave[1 ref] vKP/REFC ->(end) 1 <0> enter ->2 2 <;> nextstate(X: main 1 -e:1) v:{ ->3 3 <"> next("X") v ->4 -e syntax OK $ perl -MO=Concise -e 'X: goto X' 4 <@> leave[1 ref] vKP/REFC ->(end) 1 <0> enter ->2 2 <;> nextstate(X: main 1 -e:1) v:{ ->3 3 <"> goto("X") v ->4 -e syntax OK

Another difference is this warning here:

$ perl -wE 'sub f() { next X }; X: for (1) { f }' Exiting subroutine via next at -e line 1.

which you don't get with goto. And of course the fact that the code above terminates, but doesn't if you replace 'next' with 'goto'.

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