Precedence issues. Try replacing those '||'s with 'or's. For example, this

my $flags=fcntl $fh,F_GETFL,0 || die "fcntl call failed: $!\n";
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is being seen by the compiler as:

my $flags=fcntl $fh,F_GETFL, (0||die "fcntl call failed: $!\n");
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Dave.