You want umask.

To *get* the permissions of a file, I assume you'd want to use stat, yes, or File::stat, which gives a nice by-name interface to the stat fields. So, for example,

use File::stat;
my $st = stat "foo";
print "file is executable" if $st->mode & 0111;
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I'm not quite sure how you'd go about turning file permissions into a file creation mask (as used by umask), other than a big if/then block.