You probably just used the  "C:\Users\li\test" string as a quick example, but be aware that escapes (backslashes) in double-quoted strings are not passive. (I use  qq{...} in the following example instead of  "..." because Windoze command line doesn't like double-quotes.) The string you posted has three major pitfalls:

c:\@Work\Perl\monks>perl -wMstrict -le
"my $weird = qq{C:\Users\li\test};
 print qq{weird double-quotish interpolation '$weird'};
 ;;
 my $cool = qq{C:/Users/li/test};
 print qq{forward slashes '$cool'};
 ;;
 my $single = 'C:\Users\li\test\\';
 print qq{non-interpolating single quotes '$single'};
"
weird double-quotish interpolation 'C:SERSI     EST'
forward slashes 'C:/Users/li/test'
non-interpolating single quotes 'C:\Users\li\test\'
[download]

Perl treats forward and backward slashes in directory paths equivalently for internal use; it's usually best to use forward slashes in such paths. Also note that the final  \ (backslash) in the single-quote example must be escaped.

See Quote and Quote-like Operators.