in reply to Large File Parsing

my @items;

foreach my $key (keys %hash){
   push(@items,$key);
}

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Or simply: 

my @items = keys %hash;

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my $rxMatchItems;
{ local $" = q{|};
   $rxMatchItems = qr{(?:@items)};
}

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Or simply: 

my $rxMatchItems = do { local $" = q{|}; qr{(?:@items)} };

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Because your %hash is empty your pattern match becomes: 

$ perl -le'my @items; my $rxMatchItems = do { local $" = q{|}; qr{(?:@
+items)} }; print $rxMatchItems'
(?-xism:(?:))

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And the pattern (?-xism:(?:)) will match everything.

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Re^2: Large File Parsing
by Anonymous Monk on Jan 03, 2010 at 05:36 UTC
    my $rxMatchItems = do { local $" = q{|}; qr{(?:@items)} };

    Oh noes :) 

    my $rxMatchItems = join '|', map quotemeta, @items;
$rxMatchItems = qr/$rxMatchItems/;

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      I'm guessing from the variable name and the use of quoting constructs that the OP grabbed that bit of code from one of my solutions, probably one where @items contained values known not to need quotemeta'ing. Invariable application of quotemeta without any consideration of whether it is necessary is just another form of cargo cult programming. I don't think we can tell from the OP's code whether it is required or not. Even if it is required, the do block construct is as valid as using join.

      my $rxMatchItems = do
   {
       local $" = q{|};
       qr{(?:@{ [ map quotemeta, @items ] })};
   };

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      Cheers,

      JohnGG

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