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.

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