I've written a program which rotates atoms (with a set rotation and translation) around an axis for a Bioinformatics program I'm working on, it works going in one direction, does anyone know of a simple tweak I could do make it rotate in the opposite (anti-clockwise direction) please, which wouldn't involve me re-writing the whole program again?

sub rotator {

use Math::Vector::Real;

(*xcord, *ycord, *zcord, *BMatoms, $AxisLineUnitvector, $XlineAxis, $Y
+lineAxis, $ZlineAxis) = @_;

$angrad = 9.4;
$transl = 0.4;

use Math::Trig;

#converting deg to rad
$angrad = deg2rad($angrad);

#coefficient processing
$coefl1 = 1-cos($angrad);
$coefl2 = sin($angrad);

#Breakdown axis line vector into constituent X,Y & Z co-ordinates
($LUVx, $LUVy, $LUVz) = &VectorBreakdown($AxisLineUnitvector);

#for loop to process all atoms 
for (my $i = 0; $i < @BMatoms; $i++) {

#distances of co-ordinates to axis line
$Xco[$i] = $xcord[$i] - $XlineAxis;
$Yco[$i] = $ycord[$i] - $YlineAxis;
$Zco[$i] = $zcord[$i] - $ZlineAxis;

#convert diatance co-ordinates into a vector
$Vector[$i] = V($Xco[$i], $Yco[$i], $Zco[$i]);

#dot product
$scal[$i] = $LineUnitvector * $Vector[$i];

#scalar product
$f[$i] = ($scal[$i] * $AxisLineUnitvector) - $Vector[$i];

#dot product
$f[$i] = $coefl1 * $f[$i];

#cross product
$s[$i] = $AxisLineUnitvector x $Vector[$i];

#dot product
$s[$i] = $coefl2 * $s[$i];

#vector broken down into constituent parts
($fx[$i], $fy[$i], $fz[$i]) = &VectorBreakdown($f[$i]);
($sx[$i], $sy[$i], $sz[$i]) = &VectorBreakdown($s[$i]);

#new co-ordinates
$xo[$i] = $xcord[$i] + $fx[$i] + $sx[$i] + ($transl * $LUVx);
$yo[$i] = $ycord[$i] + $fy[$i] + $sy[$i] + ($transl * $LUVy);
$zo[$i] = $zcord[$i] + $fz[$i] + $sz[$i] + ($transl * $LUVz);

#rounding up
$xo[$i] = sprintf("%.3f",$xo[$i]);
$yo[$i] = sprintf("%.3f",$yo[$i]);
$zo[$i] = sprintf("%.3f",$zo[$i]);

}

return(\@xo, \@yo, \@zo);
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Many Thanks in advance! <\p>