It also accepts an empty string, since you've got a doubled '|' in there. One | separates alternatives, not two.

As for dumbing it down, I'd rewrite it like so: 

$A_rx = qr{ \Q $A }x;
$w_rx = qr{ \Q $w }x;

$rx = qr{
  $A_rx \s*
  \*? \s*
  cos \s*
  (?:
    \( \s* $w_rx \s* \*? \s* t \s* \)
    | $w_rx \s* \*? \s* t \s
  ) \s*
  A
}x;

[download]
Then you can use it in the following manner: $string =~ /^\s*($rx)\s*$/.
Jeff japhy Pinyan, P.L., P.M., P.O.D, X.S.: Perl, regex, and perl hacker
How can we ever be the sold short or the cheated, we who for every service have long ago been overpaid? ~~ Meister Eckhart

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

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