Regular Expression Question (insertion/substitution)

[MaxCarp]

Basically, I am trying to construct a substitute expression that accomplishes the following: given all occurrences of a certain type of string (for instance, digits), insert some prefix or suffix before or after all occurences.

For example, in the string --12***345)))6789?<>, I want to insert some prefix before the numeric substrings, to give e.g. --found12***found345)))found6789?<>

Now, the regular expression

s/[0-9]*/found/g would find all strings of digits and replace them with the word "found." However, I want to keep the substrings of numbers and insert a prefix. What do I need to do?

Thanks, Max

 

[rharsh]

The easiest way to do what you're looking for is something similar to:

$_ = '--12***345)))6789?<>';
my $prepend = $_;
$prepend =~ s/(\d+)/found${1}/g;
print "$prepend\n";
my $append = $_;
$append =~ s/(\d+)/${1}found/g;
print "$append\n";

For more information, take a look at: perldoc perlre

 

[MaxCarp]

Thank you.

Sorry for the naive question, but if I understand it correctly, the construct ${1} means taking a single instance of the regular expression and assigning it to the substring ${1}?

 

[rharsh]

You're welcome.

$1 (${1} is a different way to notate the same thing that helps differentiate the variable name from any other characters immediately after the variable) refers to the first capture group.

Here's a link to the pertinent section in perldoc perlre I mentioned above. perlre - Capture Groups

I would really suggest you take some time and read through that perlre perldoc page. A lot of it won't make sense initially but it will give you a good idea about how the regex engine works and how to construct regexs to do what you want.