bestresearch2 has asked for the wisdom of the Perl Monks concerning the following question:

I'm new to Perl. Awesome language!!! I'm having a problem with writing a matching expression. Since some of the substrings have "." in them, \b is not quite working for me. 
#!/usr/local/bin/perl

$teststr1='perl.org';
$teststr2='perl .org';

$termstr1='.org';
$termstr2='perl';

# I don't want to find 'perl' in 'perl.org'
if ($teststr1 =~ m/\b$termstr2\b/)
{
  print "uggh1\n";
}

# I don't want to find '.org' in 'perl.org'
if ($teststr1 =~ m/\b$termstr1\b/)
{
  print "uggh2\n";
}

# I DO want to find '.org' in 'perl .org'
if ($teststr2 =~ m/\b$termstr1\b/)
{
  print "hurray1\n";
}

# I DO want to find 'perl' in 'perl .org'
if ($teststr2 =~ m/\b$termstr2\b/)
{
  print "hurray2\n";
}
>...

[download]

Replies are listed 'Best First'.
Re: Help with matching .org
by moritz (Cardinal) on Jan 09, 2008 at 14:58 UTC
    Essentially you are searching for something that is delimited either by whitespaces or by end of string/line, right?

    In this case your regexp should look something like this: 

    # custom word boundary:
my $wb = qr{ ^ | $ | \s }x;

# you have to take care if you are checking for a left or a right word
+ boundary:
if ($str =~ m/(?<=$wb)$termstr1(?=$wb)/){
   ...
}

    [download]
[reply]
[d/l]
      Thanks! Delimited by whitespace, end of string/line, or beginning of string/line. Will this work for that too?
[reply]
        hmmm. Perl does not like variable length lookaround. But it seems I can get away with (the less efficient): 
        m/(^|?|\s)string(^|?|\s)/

        [download]
        Thanks for your help!!!
[reply]
[d/l]
Re: Help with matching .org
by poolpi (Hermit) on Jan 10, 2008 at 11:34 UTC
    <<Since some of the substrings have "." in them, \b is not quite working for me.>> 
    $teststr1= quotemeta 'perl.org';
# 'perl\.org'

    [download]

    HTH,
    PooLpi
[reply]
[d/l]

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