YAPE::Regex::Explain might help 
The regular expression:

(?-imsx:^\s*(\Q$A\E\s*\*?\s*\Qcos\E\s+\Q$w\E\s*\Qt\E\s+\QA\E||\Q$A\E\s
+*\*?\s*\Qcos\E\s*\(\s*\Q$w\E\s*\Qt\E\s*\)\s+\QA\E)\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))
----------------------------------------------------------------------
  (                        group and capture to \1:
----------------------------------------------------------------------
    \Q                       'Q'
----------------------------------------------------------------------
    $                        before an optional \n, and the end of
                             the string
----------------------------------------------------------------------
    A                        'A'
----------------------------------------------------------------------
    \E                       'E'
----------------------------------------------------------------------
    \s*                      whitespace (\n, \r, \t, \f, and " ") (0
                             or more times (matching the most amount
                             possible))
----------------------------------------------------------------------
    \*?                      '*' (optional (matching the most amount
                             possible))
----------------------------------------------------------------------
    \s*                      whitespace (\n, \r, \t, \f, and " ") (0
                             or more times (matching the most amount
                             possible))
----------------------------------------------------------------------
    \Q                       'Q'
----------------------------------------------------------------------
    cos                      'cos'
----------------------------------------------------------------------
    \E                       'E'
----------------------------------------------------------------------
    \s+                      whitespace (\n, \r, \t, \f, and " ") (1
                             or more times (matching the most amount
                             possible))
----------------------------------------------------------------------
    \Q                       'Q'
----------------------------------------------------------------------
    $                        before an optional \n, and the end of
                             the string
----------------------------------------------------------------------
    w                        'w'
----------------------------------------------------------------------
    \E                       'E'
----------------------------------------------------------------------
    \s*                      whitespace (\n, \r, \t, \f, and " ") (0
                             or more times (matching the most amount
                             possible))
----------------------------------------------------------------------
    \Q                       'Q'
----------------------------------------------------------------------
    t                        't'
----------------------------------------------------------------------
    \E                       'E'
----------------------------------------------------------------------
    \s+                      whitespace (\n, \r, \t, \f, and " ") (1
                             or more times (matching the most amount
                             possible))
----------------------------------------------------------------------
    \Q                       'Q'
----------------------------------------------------------------------
    A                        'A'
----------------------------------------------------------------------
    \E                       'E'
----------------------------------------------------------------------
   |                        OR
----------------------------------------------------------------------
   |                        OR
----------------------------------------------------------------------
    \Q                       'Q'
----------------------------------------------------------------------
    $                        before an optional \n, and the end of
                             the string
----------------------------------------------------------------------
    A                        'A'
----------------------------------------------------------------------
    \E                       'E'
----------------------------------------------------------------------
    \s*                      whitespace (\n, \r, \t, \f, and " ") (0
                             or more times (matching the most amount
                             possible))
----------------------------------------------------------------------
    \*?                      '*' (optional (matching the most amount
                             possible))
----------------------------------------------------------------------
    \s*                      whitespace (\n, \r, \t, \f, and " ") (0
                             or more times (matching the most amount
                             possible))
----------------------------------------------------------------------
    \Q                       'Q'
----------------------------------------------------------------------
    cos                      'cos'
----------------------------------------------------------------------
    \E                       'E'
----------------------------------------------------------------------
    \s*                      whitespace (\n, \r, \t, \f, and " ") (0
                             or more times (matching the most amount
                             possible))
----------------------------------------------------------------------
    \(                       '('
----------------------------------------------------------------------
    \s*                      whitespace (\n, \r, \t, \f, and " ") (0
                             or more times (matching the most amount
                             possible))
----------------------------------------------------------------------
    \Q                       'Q'
----------------------------------------------------------------------
    $                        before an optional \n, and the end of
                             the string
----------------------------------------------------------------------
    w                        'w'
----------------------------------------------------------------------
    \E                       'E'
----------------------------------------------------------------------
    \s*                      whitespace (\n, \r, \t, \f, and " ") (0
                             or more times (matching the most amount
                             possible))
----------------------------------------------------------------------
    \Q                       'Q'
----------------------------------------------------------------------
    t                        't'
----------------------------------------------------------------------
    \E                       'E'
----------------------------------------------------------------------
    \s*                      whitespace (\n, \r, \t, \f, and " ") (0
                             or more times (matching the most amount
                             possible))
----------------------------------------------------------------------
    \)                       ')'
----------------------------------------------------------------------
    \s+                      whitespace (\n, \r, \t, \f, and " ") (1
                             or more times (matching the most amount
                             possible))
----------------------------------------------------------------------
    \Q                       'Q'
----------------------------------------------------------------------
    A                        'A'
----------------------------------------------------------------------
    \E                       'E'
----------------------------------------------------------------------
  )                        end of \1
----------------------------------------------------------------------
  \s*                      whitespace (\n, \r, \t, \f, and " ") (0 or
                           more times (matching the most amount
                           possible))
----------------------------------------------------------------------
  $                        before an optional \n, and the end of the
                           string
----------------------------------------------------------------------
)                        end of grouping
----------------------------------------------------------------------

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In reply to Re: is there an easy way to dumb down this regular expression for me? by Anonymous Monk
in thread is there an easy way to dumb down this regular expression for me? by moltar512

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