A couple of comments. First your use of the word canvas for a ImageMagick object is slightly confusing, but it's legal. Second, I know it's just a preliminary example, but if you are going to make it into an app that will load many pictures and operate on them, you should make your IM objects global and reuse them, so you are not making new ones all the time. You can clear out an IM object with

#reuse object
undef @$IMagick_object; # clear out IM object data
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