They also fail with negative non-integers.

perl -MPOSIX=ceil -e "$n=-2.1; print($n, ' POSIX: ', ceil($n))"
# -2.1 POSIX: -2

perl -e "$n=-2.1; print($n, ' other: ', int($n) + ($n != int($n)))"
# -2.1 other: -1
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