Well, if you've got a particularly well constrained data set, then you might be able to achieve what you want without *too* much trouble. However, your example of using a string containing a semi-colon only touches on the complexity of the problem --- here's another:

my $x = do{
    print "here's an embedded statement\n";
    42;
};
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And we can imagine all sorts of complications using other quote-like mechanisms like s//statement;statement;/e or s;;;ge ... But even if you can grok all the combinations of quote-like operators and embedded multi-statement terms, you still have a problem. As merlyn so aptly points out in this node, from which I'll extract (and modify) just one little tidbit:

    $x = sin  / 25 ; # /; die "Bang! I'm dead!";
    
    $y = time / 25 ; # /; die "I'm only pretending!";
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Where does the first statement end in each of these two lines? It isn't just that you have to ignore semi-colons inside of a match operation, you have to know whether you are even in a match operation at all. Thus, while the question as you pose it may *seem* like something far less complex than actually "parsing Perl" (I just want to recognize one leading, semi-colon terminated, arbitrary statement) it really isn't at all.

And we've competely ignored other things such as many statements without terminating semi-colons(in the same vein as Beatnik mentions):

    while(<>){
        if ($. == 1){
            print "Now processing $ARGV ...\n"
        }
        print if /something/ .. /something else/
    } continue {
        close ARGV if eof
    }
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Which of course is rather contrived ... but still something to consider depending on what you are *really* trying to accomplish (although you did explicitly mention terminating semi-colons, so perhaps this isn't an issue for you).

On the other hand, I seem to recall that Simon Cozens (I think) was working on a Perl parser in Perl --- but I have no idea how far that went or what became of it.

while(1) { for(1..10) { print "foo" } print "\n" }
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For a full-featured, robust solution, you will most likely need to use Parse::RecDescent or something else.

This is, of course, a dangerous question to answer because a problem is posed without much definition of how rigorous the answer should be. Caveat emptor.

--t. alex

"Of course, you realize that this means war." -- Bugs Bunny.

I'd suggest working from the back of the statement, stripping off the trailing comment (if it exists) until you find a semi-colon. Munch the leading white space, then you're done -- for the trivial cases.

If you know where the end of the statment it, then it would have been a trivial question ;) The problem is that you can't guess where the statement ends. Even stripping commments is not a trivial task. Consider the following line:

my $foo=';'; $foo =~ s#;##g; #comments start here
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As you can see this would be tricky. I use '#' as regex delimters quite a lot. There are so many special cases in perl that you can't easily isolate things like "strip comments" or "first statement" into simple parsers.

For the origial poster, I would suggest looking at perlTidy for some ideas.



Simon Flack ($code or die)
$,=reverse'"ro_';s,$,\$,;s,$,lc ref sub{},e;$,
=~y'_"' ';eval"die";print $_,lc substr$@,0,3;

2;0 juerd@ouranos:~$ perl -e'undef christmas'
Segmentation fault
2;139 juerd@ouranos:~$
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my $firstline = (`perl -MO=Deparse $0 2>nul`)[2];
print "\nThe first line of Perl code is:\n$firstline";

# first test:
$x = sin / 25 ; # /; die "Bang! I'm dead!"; 
$y = time / 25 ; # /; die "I'm only pretending!";
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The first line of Perl code is:
$x = sin / 25 ; # /;
Bang! I'm dead! at D:\Perl\dl\debug\testsource.pl line 19.
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--
I'd like to be able to assign to an luser

($match) = $file =~ /([^\"\'\`\;]*(?:[\"\'\`]+.*[\"\'\`]+)?);/;
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rdfield