= and then ~
but don't put any whitespace between the two characters, because that's valid too, and means something entirely different! = is plain assignment and ~ is the unary bitwise not operator. So it would mean:
$_ is assigned the value of bitwise not the value of (whatever expression, in this case, how many times did the match succeed?)

In reply to Re^2: syntax error by bart
in thread syntax error by Anonymous Monk

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