Does Perl provide this functionality?

Yes. As I demonstrated above. And here again:

c:\test>perl -le"
my $n = oct( $ARGV[ 0 ] ); 
printf qq[As decimal: %d As octal: %o \n], $n, $n; 
" 0644

As decimal: 420 As octal: 644
[download]

Let me try and explain what is going on above/

1. The value '0644' is a string being supplied to the perl program as a command line argument. It shows up inside the program (the bit between double quotes here: -le"..."), as $ARGV[ 0 ].
2. $ARGV[0] is then passed to the built-in function oct, which parses that string ('0644'), and converts it to a number in perl's internal binary representation, and assigns it to the scalar variable $n.
3. Now, when you use $n, how it will be used will depend upon the context in which you use it.

   That is to say, if you use $n as a string--for example by concatenating it to another string:

   c:\test>perl -le"my $n = oct( $ARGV[ 0 ] ); print 'As a string:' . $n;
   + " 0644
   As a string:420
   [download]

   It will be converted from that internal binary representation automatically, and used as a (decimal) formatted ascii string.

   However, if you use it in a numeric context--by adding it to another number--then it will be used as a number:

   c:\test>perl -le"my $n = oct( $ARGV[ 0 ] ); print 1 + $n; " 0644
   421
   [download]

Does that clarify things for you?

I realise that if you are used to having to convert between string and numeric representations explicitly, that this automation seems unintuative and leaves you thinking you need to do more, but trust me it works.