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Re: exiting via next: Extra careful or just bitchy?

by dug (Chaplain)
on Apr 19, 2004 at 19:33 UTC ( #346425=note: print w/replies, xml ) Need Help??

in reply to exiting via next: Extra careful or just bitchy?

My guess is that you have tailored your program to work with the logic in this subroutine (or that it's an accidental success).

perldoc -f do says:
"do BLOCK" does not count as a loop, so the loop control statements "next", "last", or "redo" cannot be used to leave or restart the block. See perlsyn for alternative strategies.
More details are available in perlsyn

One way what you've written would work could be described as:

1) you repeatedly call my $line = nextline( $fh );
2) the first line of the do block reads a line off of your filehandle.
3 a) if that line is a comment, the subroutine exits via next (next doesn't go to the next iteration of the do block (as we learned from the documentation)).
3 b) if that line isn't a comment, it's assigned to $l (via clean()).
4) this happens until $l ne ''.

Since even "blank" lines will contain a newline, the until conditional will guarantee that your do block is only entered once (even for non-comment lines).

Hope that helps a little,

-- Douglas

Replies are listed 'Best First'.
Re: Re: exiting via next: Extra careful or just bitchy?
by vacant (Pilgrim) on Apr 19, 2004 at 19:40 UTC
    Yes, I think that is exactly what was happening. (Was -- I have fixed it by now.) This sub is part of a simple parser, and the caller patiently ignored the empty strings and called the sub again. Your remark about the "blank" lines not being really empty is also well noted. Actually, the clean() sub removes the newlines, which I did not mention.

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