use strict; 
use warnings; 

use YAPE::Regex::Explain;
print YAPE::Regex::Explain->new('[[\\s(/]ssshd\\s')->explain();

__END__

The regular expression:

(?-imsx:[[\s(/]ssshd\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):
----------------------------------------------------------------------
  [[\s(/]                  any character of: '[', whitespace (\n, \r,
                           \t, \f, and " "), '(', '/'
----------------------------------------------------------------------
  ssshd                    'ssshd'
----------------------------------------------------------------------
  \s                       whitespace (\n, \r, \t, \f, and " ")
----------------------------------------------------------------------
)                        end of grouping
----------------------------------------------------------------------
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This points out an interesting issue with how the OP formatted his post. Because you fed YAPE::Regex::Explain a single-quote constructed string, it saw a whitespace character, whereas when I assumed the OP had wrapped the expression directly in m<...> I expected a backslash or an 's' in the class. I think your result is likely more logical.

In regular expressions, square brackets indicate character classes. In this case you will match on any of the following list of characters:

[ \ s ( /

I'm actually a little surprised that the regular expression engine doesn't throw an error on an unescaped open square bracket in a character class, but it seems to have no problem parsing it, so...

The rest of the expression just requires the literal string ssshd\s. Thus the following outputs 1:

print '(ssshd\s' =~ m<[[\\s(/]ssshd\\s>;

I would like to echo the first paragraph of the above post.   And please don’t treat it as an “RTFM!” brush-off, because it is not.

perldoc pages are generally very well-written, and there are a great many of them which discuss regular expressions.   Some of them take a while to read, but it is time very well spent.   Regular expressions are one of the core power-tools of Perl, and these pages are the first and the best place to begin learning about them.