Question

I’ve got two question about Regexp::Common qw/URI/ and Regex in Perl.

I use Regexp::Common qw/URI/ to parse URI in the strings and delete them. But I’ve got an error when a URI is between parentheses.

For example: (http://www.example.com)

The error is caused by ‘)’, and when it try to parse the URI, the app crash. So I’ve thought two fixes:

• Do a simple (or I thought so) that writes a whitespace between parentheses and ) characters
• The Regexp::Common qw/URI/ has a function that implement a fix.

In my code I’ve tried to implement the Regex but the app freezes. The code that I’ve tried is this:

use strict;

use Regexp::Common qw/URI/;
my $str = "Hello!!, I love (http://www.example.com)";
while ($str =~ m/\)/){
                $str =~ s/\)/ \)/;
        }
my ($uri) = $str =~ /$RE{URI}{-keep}/;
print "$uri\n";
print $str;

The output that I want is: (http://www.example.com )

I’m not sure, but I think that the problem is in $str =~ s/\)/ \)/;

BTW, I’ve got a question about Regexp::Common qw/URI/. I’ve got two string type:

1. ablalbalblalblalbal http://www.example.com
2. asfasdfasdf http://www.example.com aasdfasdfasdf

I want to remove the URI if it is the last component (and save it). And, if not, save it without removing it from the text.

Answer 1

my $str = "Hello!!, I love (GOOGLE)";
while ($str =~ m/)/){
  $str =~ s/)/ )/;
}

Your program goes into an infinite loop at this point. To see why, try printing the value of $str each time round the loop.

my $str = "Hello!!, I love (GOOGLE)";
while ($str =~ m/)/){
  $str =~ s/)/ )/;
  print $str, "\n";
}

The first time it prints “Hello!!, I love (GOOGLE )”. The while loop condition is then evaluated again. Your string still matches your regular expression (it still contains a closing parenthesis) so the replacement is run again and this time it prints out “Hello!!, I love (GOOGLE )” with two spaces.

And so it goes on. Each time round the loop another space is added, but each time you still have a closing parenthesis, so another substitution is run.

The simplest solution I can see is to only match the closing parenthesis if it is preceded by a non-whitespace character (using \S).

my $str = "Hello!!, I love (GOOGLE)";
while ($str =~ m/\S)/){
  $str =~ s/)/ )/;
  print $str, "\n";
}

In this case the loop is only executed once.