comment on

Yep. Adding a print pos() inside the (?{code}) block shows that it does give the right pos values:

sub foo {
    my $window = "a b X20 c X5 d e X17 X12";
    my @o = ();
    my @m = ($window =~ m/(X\d+(?{print ">pos:",pos();push @o, pos()})
+)/g);
    print "Matches: @m";
    print "Offsets: @o";
    print " ";
}
__END__
>pos:7
>pos:12
>pos:20
>pos:24
Matches: X20 X5 X17 X12
Offsets: 7 12 20 24
 
>pos:7
>pos:12
>pos:20
>pos:24
Matches: X20 X5 X17 X12
Offsets: 
 
>pos:7
>pos:12
>pos:20
>pos:24
Matches: X20 X5 X17 X12
Offsets:
[download]

Moving the declaration of @o outside of sub foo makes it clear:

my @o = ();
sub foo {
    my $window = "a b X20 c X5 d e X17 X12";
    my @m = ($window =~ m/(X\d+(?{print ">pos:",pos();push @o, pos()})
+)/g);
    print "Matches: @m";
    print "Offsets: @o";
    print " ";
}

__END__
>pos:7
>pos:12
>pos:20
>pos:24
Matches: X20 X5 X17 X12
Offsets: 7 12 20 24
 
>pos:7
>pos:12
>pos:20
>pos:24
Matches: X20 X5 X17 X12
Offsets: 7 12 20 24 7 12 20 24
 
>pos:7
>pos:12
>pos:20
>pos:24
Matches: X20 X5 X17 X12
Offsets: 7 12 20 24 7 12 20 24 7 12 20 24
[download]

In other words, the @o in the (?{code}) block has been closed over, while the one in the print statement is a fresh array. The closed array is no longer accessible outside the regexp.

A naughty solution might be the following (abusing something of a bug in perl; this may break in future versions):

sub foo {
    my $window = "a b X20 c X5 d e X17 X12";
    my @o = () if pos; # conditional declaration makes @o "static"
    @o = (); # reset it always
    my @m = ($window =~ m/(X\d+(?{push @o, pos()}))/g);
    print "Matches: @m";
    print "Offsets: @o";
    print " ";
}

__END__
Matches: X20 X5 X17 X12
Offsets: 7 12 20 24
 
Matches: X20 X5 X17 X12
Offsets: 7 12 20 24
 
Matches: X20 X5 X17 X12
Offsets: 7 12 20 24
[download]

In reply to Re^2: Multiple uses of (?{ code }) do not appear to be called by rhesa
in thread Multiple uses of (?{ code }) do not appear to be called by bsdz

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