haukex and syphilis have already provided some good answers but I thought that I would point out some things that I didn't see mentioned.

Perl's int is not the same as C's floor(). What you want is POSIX::floor. It has the identical behavior as C's floor().

Perl has a pre-decrement just like C.

    # for(int i = len; i > 0; --i) { # C
    # for(my $i = $len; $i > 0; $i--){ # incorrect Perl
    for(my $i = $len; $i > 0; --$i){ # correct Perl
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YMMV as I haven't tried it out with these changes implemented.