Variables as pattern matching options 1

[Guest_imported]

I am doing a search through text.
The search goes in the format of:
$text =~ /$pattern/i
to make it case insensitive.
What i really want is to make it case insensitive depending on a variable.
Now I know that I COULD do it by having if clauses at every search...
but there are a LOT of searches and that would make the script inefficient.
Therefore i have the line at the top saying:
$case = "i" if ($sensitive eq "no"
$case = "" if ($sensitive eq "yes"
And i want all of my search lines (and there are a LOT) to say:
$text =~ /$pattern/$case
however it interprets it as a non scalar and falls over.
In what format, if any, an i put the $case in order to make it search with
or without
i dependent on $case without having two lines of if... else at each search.

Thanks a lot guys
Gareth
Thermeon Europe Ltd
Gbjk@carsplus.co.uk

 

[Rajoidea]

This trick depends a little on which version of perl you use. It works in the newest 5.6 stuff, and I know it dosen't work before 5.0, but in between is a grey area for me. Basically, you want to do a precompiled regular expression in your search with qr (man perl opt for more info). Assuming you have some command line option $opt_i to say case in/sensitive, it could look something like this:

$compiled_search =~ ($opt_i? qr/$pattern/i : qr/$pattern/);
#more code...
if ($text =~ $compiled_search){#do something}

Of course, your mileage may vary, but that's the jist of it. The magic to look for if you need to tweak that is qr.

Rajoidea

 

[sackyhack]

Another way to do this is to use embedded pattern-match operators (see man perlre). These work by adding a string with the pattern match parameters before the regular expression. For example (building on your code):

# $case will contain embedded pattern-match operator
$case = "(?i)" if ($sensitive eq "no");
$case = "" if ($sensitive eq "yes");

# use operator preceding regular expression
if ($text =~ /$case$pattern/) {
...
}

 

[tsdragon]

sackyhack's answer is the one I would use. That's pretty much the reason the for that extension.
Tracy Dryden
tracy@bydisn.com

Meddle not in the affairs of dragons,
For you are crunchy, and good with mustard.