Re: [OT] Perl pattern matching

[Colin Watson <cjwatson@debian.org>]

On Fri, Dec 06, 2002 at 04:53:28PM +0100, J?rg Johannes wrote:
> Here it comes:
> In "Programming Perl (german translation) there is an example for how to 
> skip lines that start with the hash sign:
> 
> LINE: while ($line = <INFILE>) {
>  next LINE if /^#/;       # Should skip lines that start with the hash 
> sign.
>  # what to do with non-comment-lines....
> }

Instead of the second line there, you need:

    next LINE if $line =~ /^#/;

... otherwise you're matching against $_, which you haven't set.

Actually that example is wrong in other ways: it'll break if you read a
line containing a false string value like "0", I think. Use one of these
instead:

  while (<INFILE>) {
    next if /^#/;
    # the input line is in $_
  }

  while (defined($line = <INFILE>)) {
    next if $line =~ /^#/;
    # the input line is in $line
  }

> PS.: The book is written for Perl 5.006, I think, and I use 5.8 (from 
> sid). Did the pattern matching change?

Nope, the example you quote is wrong in both.

Cheers,

-- 
Colin Watson                                  [cjwatson@flatline.org.uk]