#!/usr/bin/perl

use strict;
use warnings;
use YAPE::Regex::Explain;

my $re = '[Calle[-\s]/';
print YAPE::Regex::Explain->new($re)->explain;

The regular expression:

(?-imsx:[Calle[-\s]/)

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):
----------------------------------------------------------------------
  [Calle[-\s]              any character of: 'C', 'a', 'l', 'l', 'e',
                           '[''-', whitespace (\n, \r, \t, \f, and "
                           ")
----------------------------------------------------------------------
  /                        '/'
----------------------------------------------------------------------
)                        end of grouping
----------------------------------------------------------------------