What am I seeing?

33188 decimal = 100644           octal  (first printf)
07777 octal   = 0000111111111111 binary (mask)-|
                                               +- & (bitwise AND)
33188 decimal = 1000000110100100 binary (mode)-|
0644  octal   = 0000000110100100 binary (printf after mask)
                ^^^^
                  |
                  + - file type masked out
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How can store the number in a scalar rather than printing it?

use Modern::Perl;

my $mode = 33188;
my $modeResult = sprintf '%04o', $mode & 07777;

say $modeResult; # prints 0644
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