I have a similar script to pull PNG images out of Word documents. There might be edge cases, but its been Good Enough so far:

my $HEADER = "\211PNG";
my $FOOTER = "IEND\xAEB`\x82";

foreach my $file ( @ARGV )
    {
    print "Extracting $file\n";
    (my $image_base = $file) =~ s/(.*)\..*/$1/;
        
    my $data = do { local $/; open my( $fh ), $file; <$fh> };
    
    my $count = 0;
    
    while( $data =~ m/($HEADER.*?$FOOTER)/sg )
        {
        my $image      = $1;
        $count++;
        my $image_name = "$image_base.$count.png";
        open my $fh, "> $image_name" or warn "$image_name: $!", next;
        print "Writing $image_name: ", length($image), " bytes\n";
        print $fh $image;
        close $fh;
        }
        
    }
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