Re: matching / splitting within a substitution

[jsprat]

A quick trip through Deparse shows that perl changes the substitution to this:

$template =~ s[
        \[% \s+ IF \s+ (\w+) \s+ %\] # $1 var
        (.*?)                        # $2 then
        \[% \s+ END \s+ %\]
    ][do {
    my($a, $b, $c) = ($1, $2, '');
    if ($b =~ /[% \s+ ELSE \s+ %]/gsx) {
#==============^                ^      backslashes removed!
        my(@c) = split(/[%\s+ELSE\s+%]/s, $b, 2);
#=======================^            ^ backslashes removed!
        warn 'c(', join('|', @c), ')' if DEBUG;
        $b = $c[0];
        $c = $c[1];
    }
    warn "a($a) b($b) c($c)\n----\n" if DEBUG;
    defined $$v{$a} && $$v{$a} ? $b : $c;
};]egsx;

Note that the backslashes were removed from the regexes! Time for a bug report?

On a hunch, I changed the second set of delimeters from square brackets to curly brackets, the output is as you expected originally.

Update: perl 5.8.0 (ActiveState build 806) on Win2K

Update: The more I think about it, I don't consider this a bug. If you use double-quotes to delimit a string ("\"Hello\""), backwhacking the delimiter results in the double quote as part of the string. The same should hold for square brackets as a delimiter.

[PodMaster]

Thanks jsprat (and dws -- I should have tried Deparse). I do believe we have a bug, but I got a feeling it's already been reported(will search). Anyway, here is a simpler example that I might submit as a bug report (and I hope this is easy enough to follow BrowserUk).

## in the substitution part (the second half),
## the /\[B\]/ is turned into /[B]/, see results
## and deparse output at the end
my $t  = '[A] yoda [B] jeffa [C]';
$t =~ s
    {
        \[A\]
        (.*?)
        \[C\]
    }
    [
        my $r = $1;
        if( $r =~ /\[B\]/ ){
            $r =~ s/\[B\]/GOT B/;
        }
        $r;
    ]gsex;

my $o  = '[A] yoda [B] jeffa [C]';
$o =~ s
    {
        \[A\]
        (.*?)
        \[C\]
    }
    {
        my $r = $1;
        if( $r =~ /\[B\]/ ){
            $r =~ s/\[B\]/GOT B/;
        }
        $r;
    }gsex;

# happens here also, but is not significant
# since <> aren't metacharacters
my $p  = '<A> yoda <B> jeffa <C>';
$p =~ s
    {
        \<A\>
        (.*?)
        \<C\>
    }
    <
        my $r = $1;
        if( $r =~ /\<B\>/ ){
            $r =~ s/\<B\>/GOT B/;
        }
        $r;
    >gsex;

print "
$t
$o
$p
";
__END__

 yoda [GOT B] jeffa
 yoda GOT B jeffa
 yoda GOT B jeffa

# -MO=Deparse output
my $t = '[A] yoda [B] jeffa [C]';
$t =~ s[\n        \[A\]\n        (.*?)\n        \[C\]\n    ][my $r = $
+1;
if ($r =~ /[B]/) {
    $r =~ s/[B]/GOT B/;
}
$r;]egsx;
my $o = '[A] yoda [B] jeffa [C]';
$o =~ s[\n        \[A\]\n        (.*?)\n        \[C\]\n    ][my $r = $
+1;
if ($r =~ /\[B\]/) {
    $r =~ s/\[B\]/GOT B/;
}
$r;]egsx;
my $p = '<A> yoda <B> jeffa <C>';
$p =~ s[\n        <A>\n        (.*?)\n        <C>\n    ][my $r = $1;
if ($r =~ /<B>/) {
    $r =~ s/<B>/GOT B/;
}
$r;]egsx;
print "\n$t\n$o\n$p\n";

MJD says "you can't just make shit up and expect the computer to know what you mean, retardo!"

I run a Win32 PPM repository for perl 5.6.x and 5.8.x -- I take requests (README).

** The third rule of perl club is a statement of fact: pod is sexy.

[tye]

A simpler example to report is:

% perl -MO=Deparse -e "s{\[A\]}[s/\[B\]/C/g]g"
s[\[A\]][s/[B]/C/g]g;
-e syntax OK

But I don't consider it a bug. If your delimiters are [] then \[ becomes [. If you want \[ then you'll need \\\[ (or \\[ also works if the square brackets balance).

So, inside qq[], [] and \[\] are the same. Much like "\g" and "g" are the same or '\g' and '\\g' are the same.

                - tye

[PodMaster]

Ok, I think you have a point, so what I think now is that the pod needs to be enhanced to mention this. Thanks.

C:\>perl -MO=Deparse -e" s{\[A\]}'s/\[B\]/C/g'g"
s[\[A\]][s/\\[B\\]/C/g]g;
-e syntax OK

MJD says "you can't just make shit up and expect the computer to know what you mean, retardo!"

I run a Win32 PPM repository for perl 5.6.x and 5.8.x -- I take requests (README).

** The third rule of perl club is a statement of fact: pod is sexy.