in reply to Re: Perlmonks Code Proxy
in thread Perlmonks Code Proxy

I tried something like s///ge at one point, but it doesn't work in this case. The /e causes the right hand side of s/// to be handled as code to eval. Well, since we are deliberately matching Perl code with this regex, this solution tends to choke quite spectacularly.

I think its probably cause your substituting stuff into content, making the string different when it tries to do a second match...

Oh!!!!! Good point. Didn't think Perl would bomb on that. Need to go check it out. Thanks.

Cheers,
Ovid

Update: Oops. Just noticed that tye pointed out the same problem and I've verified that it's the bug. Here's a bit of sample code that can reproduce it (don't do this at home, kids): 

#!/usr/bin/perl 

$string = "1";

# Infinite loop caused by modifying the string we are matching against
+ in while statement

while ($string =~ /(\d)/g) {
    $match = $1;
    $string =~ s/$match/$match/;
}
print $string;

[download]

Update 2: After reading through Boogman and tilly's comments below, I'll have to see what I can do to reproduce the /e error. It was rather frustrating.

Replies are listed 'Best First'.
RE: RE: Re: Perlmonks Code Proxy
by Boogman (Scribe) on Aug 19, 2000 at 01:24 UTC
    The /e causes the right hand side of s/// to be handled as code to eval. Well, since we are deliberately matching Perl code with this regex, this solution tends to choke quite spectacularly.
    Hmmm... Thats strange. I decided to fool around with it and tried this out: 
    my $i = 1;
my $string = 'print "hello";';
my $content = 'print "hello";$x + 2; print "hello";print "hello";print
+ "hello";';

$content =~ s/($string)/$1.$i++."\n"/ge;

print "$content\n";

eval $string;

    [download]
    and it printed out 
    print "hello";1
$x + 2; print "hello";2
print "hello";3
print "hello";4

hello

    [download]
    It doesn't seem that it executed the print statement that was matched, even though if we hand the string directly to exec, it does print out hello.
[reply]
[d/l]
[select]
      Right hand side, not left: 
      $str = "Hello world\n";
$str =~ s/o/print "Got an o!\n"/eg;
print $str;

      [download]
[reply]
[d/l]
        yeah - I was saying that if you matched code on the right side, and then used that code in the eval expression with $1, it wouldnot get executed.

        AKA, saying s/(stuff)/$1/eg would not do anything even if the stuff captured in $1 was perl code.

        $string = "print 'got an o\n'";
$string =~ s/(.*)/$1/eg;

        [download]
        Doesn't print anything.
[reply]
[d/l]
[select]

In Section Seekers of Perl Wisdom