You can either use the Image::Magick module, or you can call identify, convert etc. using system() or backticks. Here's some code that I used to resize a bunch of images:

my ($w,$h) = (`identify '$indir/$_'` =~ /(\d+)x(\d+)/);
my $resize = ($w > $h ? "168x118" : "118x168");
system("convert -size $resize -resize $resize '$indir/$_' '$outdir/$ou
+tfile-small.jpg'") == 0 or die "Error converting";
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Using the Image::Magick module will probably make your code a bit cleaner than this, though.