underscores in directory names

[coldbohemia]

running dwimperl

i have these 2 lines as part of a perl 5 script:

my $dirstring = "dir p:/dir" . chr(95) . "001/" ;
system( $dirstring) ;

this gives me the error:
"parameter format not correct - "dir_001"

p: is a mapped drive on the intranet, and i'm running the dwimperl version of
strawberry perl 5.14.2.1
my os is microsoft xp svc pack 3.

i get the same error when i launch the script from padre editor, or from the dos command line.

the error is probably triggered by the underscore in the folder name, but
i don't know what to do about it.
anybody else seen this?
thanks