foreach $line (<FH>) {

Basically, this code tries to read all file content at once. That's what <> does when evaluated in list context. Try to read the file line by line. Saying,

while (<FH>) {
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is the same as

while (defined($_ = <FH>)) {
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In code above, <FH> is evaluated in scalar context and the <> operator will return line by line until it reaches end of file. See perlop for more detail.