perl -MYAPE::Regex::Explain -e " print YAPE::Regex::Explain->new(qr/$ARGV[0]/)->explain();" "^\s*[^\s\*=]+\s*="

##</code><code>##

The regular expression:

(?-imsx:^\s*[^\s\*=]+\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):
----------------------------------------------------------------------
  ^                        the beginning of the string
----------------------------------------------------------------------
  \s*                      whitespace (\n, \r, \t, \f, and " ") (0 or
                           more times (matching the most amount
                           possible))
----------------------------------------------------------------------
  [^\s\*=]+                any character except: whitespace (\n, \r,
                           \t, \f, and " "), '\*', '=' (1 or more
                           times (matching the most amount possible))
----------------------------------------------------------------------
  \s*                      whitespace (\n, \r, \t, \f, and " ") (0 or
                           more times (matching the most amount
                           possible))
----------------------------------------------------------------------
  =                        '='
----------------------------------------------------------------------
)                        end of grouping
----------------------------------------------------------------------


##</code><code>##

The regular expression:

(?-imsx:^\s*\w+\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):
----------------------------------------------------------------------
  ^                        the beginning of the string
----------------------------------------------------------------------
  \s*                      whitespace (\n, \r, \t, \f, and " ") (0 or
                           more times (matching the most amount
                           possible))
----------------------------------------------------------------------
  \w+                      word characters (a-z, A-Z, 0-9, _) (1 or
                           more times (matching the most amount
                           possible))
----------------------------------------------------------------------
  \s*                      whitespace (\n, \r, \t, \f, and " ") (0 or
                           more times (matching the most amount
                           possible))
----------------------------------------------------------------------
  =                        '='
----------------------------------------------------------------------
)                        end of grouping
----------------------------------------------------------------------

##</code><code>##

perl -MYAPE::Regex::Explain -e " print YAPE::Regex::Explain->new(qr/$ARGV[0]/)->explain();" "[^\s\*=]"
..
----------------------------------------------------------------------
  [^\s\*=]                 any character except: whitespace (\n, \r,
                           \t, \f, and " "), '\*', '='
----------------------------------------------------------------------

perl -MYAPE::Regex::Explain -e " print YAPE::Regex::Explain->new(qr/$ARGV[0]/)->explain();" "\w"
..
----------------------------------------------------------------------
  \w                       word characters (a-z, A-Z, 0-9, _)
----------------------------------------------------------------------