Something like this ought to do it.

Update: Fixed a couple of typos. And, having defined VERSION_33 in an arbitrary place in GD.xs and re-built GD, it now works.

#! perl -slw
use strict;
use GD;

our $A ||= 45;

my $imgIn = GD::Image->new( $ARGV[ 0 ] ) or die $!;
my $cx = int $imgIn->width / 2;
my $cy = int $imgIn->height /2;

my $imgOut = GD::Image->new( $imgIn->getBounds, 1 );
$imgOut->copyRotated( $imgIn, $cx, $cy, 0, 0, $imgIn->getBounds, $A );

(my $ofile = $ARGV[0]) =~s[(\..*?$)][.r$A$1];

open OUT, '>:raw', $ofile or die $!;
print OUT $imgOut->png;
close OUT;

system $ofile;
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However, despite having installed the latest versions of GD(2.28) and libgd (2.0.33), running this dies with

libgd 2.0.33 or higher required for copyRotated support at ...
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which is coming from gd.xs

void
gdcopyRotated(dst,src,dstX,dstY,srcX,srcY,srcW,srcH,angle)
        GD::Image       dst
GD::Imagesrc
        double          dstX
        double          dstY
        int             srcX
        int             srcY
        int             srcW
        int             srcH
        int             angle
PROTOTYPE: $$$$$$$$$
CODE:
{
#ifdef VERSION_33
        gdImageCopyRotated(dst,src,dstX,dstY,srcX,srcY,srcW,srcH,angle
+);
#else
        die("libgd 2.0.33 or higher required for copyRotated support")
+;
#endif
}
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but I can't work out where VERSION_33 should be defined?