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Care must be used if one is to say [...] they can be used "interchangeably".

The keywords can be used interchangeably. Any difference is purely stylistic.

Anyhow, I'm interested in why Perl has the two styles of "for" constructs

Three kinds of loops use for/foreach as far as I'm concerned:

  • Counting loop: for[each] [VAR] (EXPR .. EXPR)
  • Iterative loop: for[each] [VAR] (LIST)
  • C-style for loop: for[each] (EXPR; EXPR; EXPR)

The following iterative loops are optimised in one way or another:

  • for[each] (@array)
  • for[each] (reverse @array)
  • for[each] (reverse EXPR .. EXPR)
  • for[each] (reverse CONST_EXPR .. CONST_EXPR)

"For" looks to behave differently depending on it's context: c-style vs. (er) foreach-style. If one uses c-style "for" loops you don't always get localised indexing variables as you seem to in "foreach" loops.

That's either unclear or wrong.

C-style for loops (whether written with for or foreach) don't localise the index variable simply because they don't accept an index variable.

However, you are free to declare variables in all three of its control expressions, and they will be scoped to the loop.


In reply to Re: For vs. Foreach by ikegami
in thread For vs. Foreach by mattford63

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