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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