#!/usr/bin/perl
use strict;
use warnings;

my $path_before = qx(/home/user/Downloads/PythonProject/test.py 2>&1);
print "Befofe: " . $path_before;

my $path_new = $path_before;
$path_new =~ s{/}{\\}g; # Use s/\\/\//g;
print "After: " . $path_new;

__END__

perl test_2.pl
Befofe: /home/user/.local
After: \home\user\.local