use warnings;
use strict;
use File::Basename;

my $file = 'http://txs.corp.com:8080/area/es/2215.csv.gz';
my $gzip = basename($file, qr/\.gz/);
print "$gzip\n";

__END__

2215.csv.gz

##</code><code>##

The regular expression:

(?-imsx:/(.*?\.gz)$)

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:
----------------------------------------------------------------------
    .*?                      any character except \n (0 or more times
                             (matching the least amount possible))
----------------------------------------------------------------------
    \.                       '.'
----------------------------------------------------------------------
    gz                       'gz'
----------------------------------------------------------------------
  )                        end of \1
----------------------------------------------------------------------
  $                        before an optional \n, and the end of the
                           string
----------------------------------------------------------------------
)                        end of grouping
----------------------------------------------------------------------