Best shot, given the poorly-posed question...
use strict;
# Single quote string, and back-whack the backslashes
# to avoid misinterpretation (by readers, if not by perl).
my $strInputFileName = 'D:\\direcorty\\file.ext';
# Globally replace backslashes with four backslashes.
# Note that these all need backwhacking too, since
# regex acts somewhat like a quoted string.
$strInputFileName =~ s{\\}{\\\\\\\\}g;
I don't know what you're doing with the escaped quotes though. Also, it's directory, not 'direcorty'.