Perl Range operator question

jhuijsing has asked for the wisdom of the Perl Monks concerning the following question:

With the following code

open( IP_FH, "test.txt" );

while (<IP_FH>) {
    if ( /ABCD/ ... /EFGH/ ) {
        $match = 1;
        $found  .= $_;
    }
    else {
      if ( $match ) {
          $match = 0  ;
          print "========\n";
          print $found;
          $found = ();
      }
   }
}
[download]

and the test.txt file contains script works as expected

ABCD
122132
12
312
EFGH
FRED
ABCD
sadasd
asd
das
EFGH
FRED
ABCD
asdasd
d
as
EFGH
[download]

but when test.txt contains the text below it fails

ABCD
122132
12
312
EFGH
ABCD
sadasd
asd
das
EFGH
ABCD
asdasd
d
as
EFGH
[download]

Comment on Perl Range operator question Select or Download Code

Replies are listed 'Best First'.
Re: Perl Range operator question by ikegami (Patriarch) on Jul 08, 2010 at 05:18 UTC
The flip-flop operator returns a special value when the flop condition is true. Take advantage of it to determine that it's time to process what you have accumulated. `my $found; while (<>) { my $i = /ABCD/ ... /EFGH/; if ($i) { $found .= $_; if ($i =~ /E/) { print "========\n"; print $found; $found = ''; } } }` [download] You can also achieve the same with the following: `while (<>) { my $i = /ABCD/ ... /EFGH/; print "========\n" if $i == 1; print if $i; }` [download]	[reply] [d/l] [select]
Re: Perl Range operator question by jwkrahn (Abbot) on Jul 08, 2010 at 05:08 UTC
The `else` clause of your `if` statement will never execute if `ABCD` immediately follows `EFGH`. Try it like this instead: `open IP_FH, '<', 'test.txt' or die "Cannot open 'test.txt' $!"; my ( $match, $found ); while ( <IP_FH> ) { if ( /ABCD/ ... /EFGH/ ) { $match = 1; $found .= $_; } if ( $match ) { $match = 0 ; print "========\n"; print $found; $found = ''; } }` [download]	[reply] [d/l] [select]
Re^2: Perl Range operator question by jhuijsing (Acolyte) on Jul 09, 2010 at 00:08 UTC
Thanks for the responses Problems you find when you try to reuse code. That I wrote 7 years, when I first started to use Perl.	[reply]
Re: Perl Range operator question by afoken (Chancellor) on Jul 08, 2010 at 04:56 UTC
Explain "fails". What happens, what do you expect to happen instead? Add `use strict; use warnings;` to your code. Add error checks to your code (`open ... or die "... $!"` or `use autodie qw(:all);`). Alexander -- Today I will gladly share my knowledge and experience, for there are no sweeter words than "I told you so". ;-)	[reply] [d/l] [select]