In replying to a 6-yr old node, your question is in danger of flying beneath everyone's radar. Better to post under Seekers of Perl Wisdom. To get an idea of how this site works, I recommend looking at the "Welcome to the Monastery" section of the Tutorials page.

You might wish to check out some of the references listed here: Re: regexp: extracting info

In your example, it sounds to me more like you are trying to match the literal string "en". But let's assume for a moment you really want a character class...

One of the tools I didn't mention in the writeup above is the simple "patten test" program from Learning Perl, 3rd Ed. I often use this when first constructing a regex because it's simple, easy to edit, and I get immediate feedback. So let's start with that program, modified slightly to match the character class [en] .

# From: Schwartz & Phoenix: Learning Perl, 3rd Ed (The Llama), pp. 103

use strict;

while (<>) {
    chomp;
    if (/[en]/) {
    print "Matched: |$`<$&>$'|\n";
    } else {
    print "No match.\n";
    }
}
[download]

Let's assume that this is our "test" file:

English
French
Spanish
German
Aramaic
Arabic
[download]

Where and how the character class matches may surprise you:

Matched: |E<n>glish|
Matched: |Fr<e>nch|
Matched: |Spa<n>ish|
Matched: |G<e>rman|
No match.
No match.
No match.
[download]

If you were expecting output more like the following, matching the string "en":

No match.
Matched: |Fr<en>ch|
No match.
No match.
No match.
No match.
No match.
[download]

You will need to change the program as follows:

# From: Schwartz & Phoenix: Learning Perl, 3rd Ed (The Llama), pp. 103

use strict;

while (<>) {
    chomp;
    if (/en/) {
    print "Matched: |$`<$&>$'|\n";
    } else {
    print "No match.\n";
    }
}
[download]

HTH,