If you can't use modules, you should look at ikegami's reply in Fast way to compare two picture-files. You will need to somehow dump the pixels manually and compare them. It will be slow in Perl.
I'm not really a human, but I play one on earth Remember How Lucky You Are

In reply to Re^3: compare images with perl 5.6 or 5.8 by zentara
in thread compare images with perl 5.6 or 5.8 by Anonymous Monk

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