Why cant regex parse this string?

jayto has asked for the wisdom of the Perl Monks concerning the following question:

Alright Monks, so I made a subroutine that is supposed to break down links into 3 pieces, the domain,the path,and filename. The subroutine works for most urls:

sub createStruct{
    my %song = ();
    my $orig_url = $song{url} = shift;
    my $url = URI->new( "$orig_url" );
    my $domain = $song{domain} = $url->host;
    my @split_url = split('/',$url);
    my $filename = $song{filename} = $split_url[-1]; 
    $orig_url = $url; 
    $orig_url =~ s/$domain//g;
    $orig_url =~ s/$filename//g;
    $orig_url =~ s/http:\/\/|https:\/\/|ftp:\/\///g;
    my $dir = $song{dir} = $orig_url;
    return \%song;
}
[download]

but when I pass this url into the subroutine, it cannot remove the filename from the original url. This is the URL: http://freemp3files.hostoi.com/mp3_6744/Club SoundZ We Vol.15 (2010).mp3 This is the line that doesnt work : $orig_url =~ s/$filename//g; Why cant the filename be removed for this particular url?

Comment on Why cant regex parse this string? Download Code

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Re: Why cant regex parse this string? by moritz (Cardinal) on Jul 12, 2012 at 13:57 UTC
`$filename` is a string, but if you use it in a regex, it is interpreted as a regex. So all sorts of characters (like parenthesis, for example) have a special meaning. To prevent that, use `s/\Q$filename\E//`. See perlre for more information. But, you are already using the URI module, why do you do all those path manipulations yourself? `$url->path` gives you the path, which is the URL without schema or domain name, so you don't have to manually remove that from the original URL. Or `path_segments`, which gives you the different parts of the path delimited by slashes: `# untested: my @path_chunks = $url->path_segments; pop @path_chunks; # remove the last one, which is the file name my $dir = $song{dir} = join '/', @path_chunks;` [download] (Updated to use `$uri->path_segments`, daxim++, and s/shift/pop/, johngg++) Perl 6 - the future is here, just unevenly distributed	[reply] [d/l] [select]
Re^2: Why cant regex parse this string? by jayto (Acolyte) on Jul 12, 2012 at 14:08 UTC
Thank you, that is what I suspected the problem was, but i wasn't sure how to fix it. I also used URI->path() instead of those lines of regex that i had before. Thanks again!	[reply]