On Mon, Sep 26, 2005 at 05:00:00PM -0400, David Storrs wrote: > > On Sep 26, 2005, at 4:19 PM, Juerd wrote: > >Perl 5's $& is inefficient because of this. If the variable is used > >anywhere, Perl will for every regex used capture everything. > > My understanding is that this died with 5.10. Is that right?
$& is dynamically scoped (rather than lexically scoped). I don't believe that it's possible to avoid capturing it anywhere, without affecting correctness somehow. There is already an optimisation to avoid capturing it if $& is never seen, but even that is actually buggy: $ perl -lwe '$_ = "trouble"; /o/; print eval q.$&.' Use of uninitialized value in print at -e line 1. compare with $ perl -lwe '$&; $_ = "trouble"; /o/; print eval q.$&.' Useless use of a variable in void context at -e line 1. o where by mentioning $& I set the "seen $& somewhere" flag, so $& is captured, and it's there when the '' eval gets compiled at run time. IIRC the perl 6 equivalents of $` $& and $' are all lexical rather than dynamic, so the pain will be far less. (at least in its scope) Nicholas Clark
