As bart points out, it can't happen. It could be the shell that trying to replace what it considers special (meta) characters in the $string. You can use quotemeta to escape those characters or using the equivalent escape sequences such as \Q.

$ ls
hello
$ perl -e 'my $dir = q(not$socooldir); system "mkdir $dir" and die "ex
+ecution failed\n"'
$ ls
hello  not
$ perl -e 'my $dir = q(not$socooldir); $dir = quotemeta $dir; system "
+mkdir $dir" and die "execution failed\n"'
$ ls
hello  not  not$socooldir
$ perl -e 'my $dir = q(not$socooldir); system "mkdir \Q$dir" and die "
+execution failed\n"'
mkdir: cannot create directory `not$socooldir': File exists
execution failed
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Of course, perl has its own mkdir function, internally. Please note that the third execution fails because directory already exists, indicating that \Q$dir and quotemeta $dir result in the same directory name.

One more thing, please don't use `shellcmd args` in void context, because you ask for something to return but effectively discard it. Assign it to a scalar or an array to capture the output if you want it so.

my @lines = `shellcmd args`; # list context
my $line = `shellcmd args`; # scalar context
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