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Re: Speed of Perl Regex Engine

by Jenda (Abbot)
on Nov 29, 2012 at 16:43 UTC ( #1006298=note: print w/ replies, xml ) Need Help??


in reply to Speed of Perl Regex Engine

You said you build the regex and pass it to the program as a parameter ... how do you use it then?

my $regexp = @ARGV[1]; ... next if ($global =~ /$regexp/); ...
my $regexp = @ARGV[1]; ... next if ($global =~ /$regexp/o); ...
my $regexp = qr/@ARGV[1]/; ... next if ($global =~ $regexp); ...

The first version compiles the regexp each time you use it, the other two just once. For a longer regexp this may make a big difference.

Jenda
Enoch was right!
Enjoy the last years of Rome.


Comment on Re: Speed of Perl Regex Engine
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Re^2: Speed of Perl Regex Engine
by runrig (Abbot) on Nov 29, 2012 at 19:30 UTC
    I believe in later versions of Perl (>= 5.6), this is no longer true. As long as $regexp doesn't change, /$regexp/ isn't compiled again, making "/o" (mostly) obsolete.

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