You might want to look into PerlMagick - the Object Oriented interface to the ImageMagick goodness.

Here's the PerlMagick way to do what you're doing. It will also give you some better error handling.

use Image::Magick;

my $photo = Image::Magick->new();
my $x = $photo->ReadImage($input);
if ($x) {
  warn $x; 
  # This will catch any bad files or serious errors in reading the ima
+ge
}

my ($height, $width) = $photo->Get('height','width');
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You can find your other attributes here on the PerlMagick page.