First of all, marto is right that you don't need to call an external command for this, there is mkdir, and also make_path from the core module File::Path (Update: which can do the equivalent of mkdir -p). For proper handling of filenames, see the core module File::Spec, or, with a nicer interface, Path::Class from CPAN.

use File::Spec::Functions qw/catdir/;
use File::Path qw/make_path/;

make_path(catdir('folderA','folderB','folderC'));

# Update 2: OR:
use Path::Class qw/dir/;
dir('folderA','folderB','folderC')->mkpath;
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Only for the sake of completeness: I wrote about different ways to call external commmands (safely) at length here.