and store them in a scalar in binary. e.g. "0755"

First, in a binary computer, all data is stored "in binary".    So what specifically do you mean by "binary" in this instance?

Second, the number 0744 is the octal representation of the number 484:

$ perl -le'print 0744'
484
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Perhaps you should read the perlnumber man page to see how Perl deals with numbers, and come back here with any follow-up questions.