To futher wazat’s reply to hippo’s reply… You can write bare octal numbers in perl with a leading zero. perldoc chmod has some examples.

moo@cow[18]~>touch bingo
moo@cow[19]~>ls -laF bingo
-rw-rw-r--  1 moo  staff  0 Aug 14 22:31 bingo
moo@cow[20]~>perl -E 'chmod 0624, "bingo"'
moo@cow[21]~>ls -laF bingo
-rw--w-r--  1 apv  staff  0 Aug 14 22:31 bingo
moo@cow[22]~>perl -E 'say 0755; printf "%o\n", 493'
493
755
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