Getting Error in character class

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

Monks, i have some question in regex. Today when i was doing simple clean up work in xml file, i got the following error. But i was surprised to see that i don't find any error in the code. When i enclosed that character class in the bracket, i am not getting any error. Below i have placed a part of the code and sample input string. This is the first time i am facing such error. Is it my mistake in the code or some other issue behind it? Could anyone explain where am i going wrong.

The error i am getting:

syntax error at D:\testing\pract.pl line 14, near "[^"
Execution of D:\testing\pract.pl aborted due to compilation errors.
[download]


use strict;
use warnings;

my %imlre = ('RE1' => ['RE1', 'body', 'measure', 'remove'], 'RE2' => [
+'RE2', 'jcode', '', 'remove']);

my $input = '<front>front matter comes here</front><body>bodymatter co
+mes here</body><back>back matter</back>';

for (keys %imlre)
{

    if ($imlre{$_}->[3] =~ /^remove$/i)
    {
        $input =~ s/<$imlre{$_}->[1][^>]*>//g ; #here getting error
        #$input =~ s/<$imlre{$_}->[1]([^>]*)>//g ; #here no error
    }
}

print $input;
[download]

Prasad

Comment on Getting Error in character class - Regex Select or Download Code

Replies are listed 'Best First'.
Re: Getting Error in character class - Regex by davidrw (Prior) on Apr 03, 2006 at 15:38 UTC
it's the array access that's causing the problems.. this works around it: `my $s = $imlre{$_}->[1]; $input =~ s/<$s[^>]*>//g ;` [download]	[reply] [d/l]
Re^2: Getting Error in character class - Regex by ikegami (Patriarch) on Apr 03, 2006 at 15:40 UTC
Curlies can be used for disambiguation: `$input =~ s/<${imlre{$_}->[1]}[^>]>//g ;` [download] When dealing with HoA, HoH, AoA and AoH, the arrays are optional between the indexes. `$imlre{$_}->[1]` is the same thing as `$imlre{$_}[1]` When Perl sees `$imlre{$_}->[1][^>]` it thinks you mean `$imlre{$_}->[1]->[^>]` rather than a HoA followed by a regexp. Between the square brackets, an index is expected. Since `^>` is not a valid perl expression, you get an error. Update*: Rearranged explanation for clarity.	[reply] [d/l] [select]
Re: Getting Error in character class - Regex by holli (Abbot) on Apr 03, 2006 at 15:42 UTC
That's because perl parses the part `${imlre{$_}->[1][^>]` as `${imlre{$_}->[1]->[^>]`, hence an attempt to access an array of arrays. This of course cannot work because "^>" ~~is not numeric~~ isn't a valid Perl expression (that should resolve to something numeric). You must resolve this abiguity eg like you did in `s/<$imlre{$_}->[1]([^>])>//g`. Here the () help the perl parser to DWIM. Update:* Followed ikegami's nit picking ;) holli, /regexed monk/	[reply] [d/l] [select]
Re^2: Getting Error in character class - Regex by ikegami (Patriarch) on Apr 03, 2006 at 15:50 UTC
It doesn't have to be numeric. Just a valid Perl expression. `^[` is not a valid Perl expression.	[reply] [d/l]
Re: Getting Error in character class - Regex by murugu (Curate) on Apr 03, 2006 at 15:52 UTC
Adding a space between two [] worked fine for me. This may be due to the fact that perl tries to parse the second '[]' as extra dimension. Monks, if wrong please correct me. `use strict; use warnings; my %imlre = ('RE1' => ['RE1', 'body', 'measure', 'remove'], 'RE2' => [ +'RE2', 'jcode', '', 'remove']); my $input = '<front>front matter comes here</front><body>bodymatter co +mes here</body><back>back matter</back>'; for (keys %imlre) { if ($imlre{$_}->[3] =~ /^remove$/i) { $input =~ s/<$imlre{$_}->[1] [^>]>//xg ; #here getting error #$input =~ s/<$imlre{$_}->[1]([^>])>//g ; #here no error } } print $input;` [download] Regards, Murugesan Kandasamy use perl for(;;);	[reply] [d/l]
Re: Getting Error in character class - Regex by codeacrobat (Chaplain) on Apr 03, 2006 at 15:46 UTC
You have to specify the end of the hashref `$input =~ s/<${imlre{$_}->[1]}[^>]*>//g` as there is ambiguity for brackets in the regex.	[reply] [d/l]


go ahead... be a heretic
	PerlMonks

Getting Error in character class - Regex