I'm using XML::Simple, and I want to use the ForceArray option to the XMLin method. ForceArray accepts three types of values: 1 (to force all nested elements to be represented as arrays), a compiled regular expression (any matching element names will be forced into an array representation), or a list of element names and/or compiled regular expressions. In my situation, I want all element names starting with an uppercase letter to be forced into an array representation, except those whose name ends with either '_Flags' or '_Info'. The follwing works just fine if I want just one of the exceptions: qr/^[A-Z].*(?<!_Flags)$/. Unfortunately, the obvious extension (qr/^[A-Z].*(?<!_(?:Flags|Info))$/) fails with the error "Variable length lookbehind not implemented in regex". I've searched for ways around this, but none of the usual work-arounds fits this situation. I've tried several other regular expressions, but none of them work.

#!/bin/perl

%desired = (
        Port => 1,
        Port_Aliases => 1,
        Port_Flags => undef,
        Port_Info => undef,
        name => undef,
);

foreach $r (
        q/^[A-Z].*(?<!_Flags)$/,
        q/^[A-Z].*(?!_Flags$)/,
        q/^[A-Z].*(?(?=_Flags)\s$|$)/,
        q/^[A-Z].*((?<!_Flags)|(?<!_Info))$/,
        q/^[A-Z].*((?!_Flags$)|($!_Info$))$/,
        q/^[A-Z].*((?>_(Flags|Info))\s|)$/,
        q/^[A-Z].*(?<!_(?:Flags|Info))$/,
        ) {
        print "\ntesting /$r/\n";
        foreach (sort keys %desired) {
                $expected = $desired{$_};
                $result = /$r/x;
                $msg = ($result == $expected) ? 'ok' : 'ng';
                print "'$_'\t$msg, got '$result', expected '$expected'
+\n";
        }
}

[download]

Does anyone have any ideas? Setting ForceArray to a list of names isn't really an option, as there are several hundred possibilities. Thanks!

In reply to Variable length lookbehind not implemented in regex by samwyse

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