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The typical method is to dynamically build an alternation RE and let the RE engine do all the optimisation and hard work in lovingly hand optimised C. We use qr// so the RE is compiled once and avoid vast numbers of hash lookups, functionally useless variable assignments*, and RE compiles that you are doing above. As a general rule loops are great territory for optimisation due to the repeated execution of the loop code.

my @terms = qw( foo bar baz fool foolish ); my $re = join '|', map{quotemeta} sort {length($b)<=>length($a)}@terms +; $re = qr/($re)/; while(<DATA>){ my @matches = $_ =~ m/$re/g; next unless @matches; print "Got @matches\n" } __DATA__ Only a foobar foolish fool skips the sort by length Without this foo you look foolish and may match short elements!

Hash lookup tables may still have a place to convert a matched value into something else. Here is a trivial example. Beware /i as you need to lc($1) and use all lowercase keys in %terms or you won't get a match/lookup.

my %terms = ( foo => 'FOO', bar => 'BAR' ); my $re = join '|', map{quotemeta} sort {length($b)<=>length($a)}keys % +terms; $re = qr/($re)/i; while(<DATA>){ s/$re/$terms{lc($1)}/g; print; } __DATA__ foo is a word Bar ba blacksheep

cheers

tachyon


In reply to Re: Matching against list of patterns by tachyon
in thread Matching against list of patterns by Eyck

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