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

I am trying to replace a single character in a word with wild character and ended up with error

Here is my code

my $test = "Here is the there";
$test =~s/(ther*)/\<test\>$1\<\/test\>/ig;
print "$test\n";

[download]

The output is "Here is <test>the</test> <test>the</test>re"

But the expected output is "Here is the <test>there</test>

My intention is this * need to represent a character after the string ther.

Replies are listed 'Best First'.
Re: Wild card in regular expression
by davido (Cardinal) on Nov 28, 2012 at 21:09 UTC

    * isn't a "wildcard" for Perl regular expressions. Your regex is saying "match and capture 'the' plus zero or more 'r' characters". Consequently, the first 'the' matches.

    Try using s/(ther.*)\b/......., for example. "Dot" (.) is the wildcard metacharacter; it matches anything except for a newline, unless you ask Perl to allow it to match the newline too.

    Update: Just in case anyone stumbles across this thread while searching for an answer:

    Reading perlrequick is a great quick-start to regular expression syntax. Follow it up with perlretut, and then perlre. Additional useful resources include perlop, perlvar, perlrecharclass, perluniprops. But perlrequick is about a half hour of reading for a 70% better understanding of regexes. Each additional document adds a few extra percentage points of knowledge to the foundation that perlrequick builds. ...and of course for the 1000% bonus, "Mastering Regular Expressions" (O'Reilly).


    Dave

[reply]
[d/l]
[select]
Re: Wild card in regular expression
by moritz (Cardinal) on Nov 28, 2012 at 21:09 UTC
[reply]
[d/l]
[select]
Re: Wild card in regular expression
by toolic (Bishop) on Nov 28, 2012 at 21:14 UTC

    Tip #9 from the Basic debugging checklist : YAPE::Regex::Explain 

    The regular expression:

(?-imsx:(ther*))

matches as follows:
  
NODE                     EXPLANATION
----------------------------------------------------------------------
(?-imsx:                 group, but do not capture (case-sensitive)
                         (with ^ and $ matching normally) (with . not
                         matching \n) (matching whitespace and #
                         normally):
----------------------------------------------------------------------
  (                        group and capture to \1:
----------------------------------------------------------------------
    the                      'the'
----------------------------------------------------------------------
    r*                       'r' (0 or more times (matching the most
                             amount possible))
----------------------------------------------------------------------
  )                        end of \1
----------------------------------------------------------------------
)                        end of grouping
----------------------------------------------------------------------

    [download]

    Use . instead. Also, with different delimiters, you can clean up the replacement string: 

    use warnings;
use strict;

my $test = "Here is the there";
$test =~ s{(ther.)}{<test>$1</test>}ig;
print "$test\n";

__END__

Here is the <test>there</test>

    [download]
[reply]
[d/l]
[select]

Back to Seekers of Perl Wisdom