Perl Regular Expressions: Question mark isn't greedily matching.

Question

$var = 'about/';
$var =~ s/^(.*)\/?$/index.php?action=$1/;

I want it to match and substitute the trailing slash. But it isn't, I'm getting this result:

index.php?action=about/

What am I doing wrong? I've tried wrapping it in parenthesis (\/)? and including the question mark in the parenthesis (\/?). Not including the preceding forward slash obviously doesn't do me any good. So how can I get it to eat the slash when it's there?

Answer 1

Your problem is, that the .* is greedy as well. Try using .*?.

The Regex engine is first expanding .* as far as possible, then checks if the regex can match the input. In your case, it does, since the trailing slash is optional. It then goes home satisfied.

Answer 2

Make .* ungreedy :

$var = 'about/';
$var =~ s!^(.*?)/?$!index.php?action=$1!;

Answer 3

In your substitution, you're trying really hard to specify what you keep. It's much easier in this case to get rid of what you don't want. When a feature seems hard to use for your application, that's a sign that you're using the wrong feature.

It looks like you want to do is remove the last / in a string. So, just remove the last /:

 my $path = 'about/';
 $path = s|/\z||;

 my $action = "index.php?action=$path";

If you really wanted to do this in-place (a dubious goal), you could just do this:

 ( my $action = "index.php?action=$path" ) =~ s|/\z||;