G'day songmaster,

As LanX alluded to in his update, I suspect the /o modifier may be the issue: it certainly stood out as I read through the code fragments you provided.

In "perlre: Modifiers" you'll see:

"o  - pretend to optimize your code, but actually introduce bugs"

That provides a link to further information in "perlop: Regexp Quote-Like Operators" but the fragment identifier (#s%2fPATTERN%2fREPLACEMENT%2fmsixpodualngcer) is wrong. The closest to that is probably #s/_PATTERN_/_REPLACEMENT_/msixpodualngcer; however, the one with the most information about /o, and probably more appropriate given the code you've shown, is #m/_PATTERN_/msixpodualngc, which culminates in:

"The bottom line is that using /o is almost never a good idea."

I probably would have created all of those regexes at compile time, and I would have used my instead of our variables. A dispatch table with actions based on matches may also be appropriate.

You don't show sufficient code to make any direct modification recommendations. The following script simply suggests a technique you could adapt to your needs. 

#!/usr/bin/env perl

use strict;
use warnings;

my %capture;

BEGIN {
    my $RXone   = qr{(?x: 1 )};
    my $RXthree = qr{(?x: 3 )};
    my $RXnum   = qr{(?x: $RXone | $RXthree )};
    my $RXstr   = qr{(?x: ( [a-z]+ $RXnum ) )};

    %capture = (
        menu   => {
            regexp => qr{(?x: ^ menu   \s+ $RXstr $ )},
            action => sub { parse_menu(@_) },
        },
        driver => {
            regexp => qr{(?x: ^ driver \s+ $RXstr $ )},
            action => sub { parse_driver(@_) },
        },
    );
}

my @capture_keys = keys %capture;

while (<DATA>) {
    for my $capture_key (@capture_keys) {
        if (/$capture{$capture_key}{regexp}/) {
            $capture{$capture_key}{action}->($1);
            last;
        } 
    }
}

sub parse_menu   { print "MENU:   @_\n" }
sub parse_driver { print "DRIVER: @_\n" }

__DATA__
menu menu1
driver driver1
other other1
menu menu2
driver driver2
other other2
menu menu3
driver driver3
other other3

[download]

You may have sufficient, up-front knowledge about those "capture keys" to predefine an ordered @capture_keys rather than relying on the random list returned by keys.

Output from a sample run of that script:

MENU:   menu1
DRIVER: driver1
MENU:   menu3
DRIVER: driver3

[download]

Update (minor code alteration): My original code had $capure_key (missing "t") throughout. I've changed that to $capture_key globally; retested; output unchanged.

— Ken

In reply to Re: Parser Performance Question by kcott
in thread Parser Performance Question by songmaster

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