Help!

If I use the construct (?(condition)yes-pattern) in a regex, and the condition is (?{1}), i.e. always true, the output is as expected:

my $str = 'bxAybz';

while ( $str =~ /(?(?{1})(b[xyz]))/g ) {
    say 'yes';
    say $1;
}

--output:--
yes
bx
yes
bz

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But when I use the condition (?{pos() % 2 == 0}), I expect the same output, but I don't get it:

my $str = 'bxAybz';

while ( $str =~ /(?(?{pos() % 2 == 0})(b[xyz]))/g ) {
    say 'yes';
    say $1;
}

--output:--
yes
bx
yes
Use of uninitialized value $1 in say at 2.pl line 9.

yes
bz

[download]

Three matches?

Also, I notice the x modifier doesn't work with a conditional pattern:


my $str = 'bxAybz';

while ( $str =~ /
    (?
        (?{1})
        (b[xyz])
    )
/gx ) {
    say 'yes';
    say $1;
}


--output:--
Sequence (?
...) not recognized in regex; marked by <-- HERE in m/
    (?
 <-- HERE         (?{1})
        (b[xyz])
    )
/ at 2.pl line 12.

[download]

In reply to Re: A regex that only matches at offset that are multiples of a given N? by 7stud
in thread A regex that only matches at offset that are multiples of a given N? by BrowserUk

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