Welcome !
Please read the "File Input and Output" section of this site's tutorial on Input and Output.

To understand why you need to escape backslashes, please read the documentation on string "interpolation".

Basically, if you use double-quotes ("), the backslash(\) is the escape character. If you want to use that in the string, it needs to be doubled up.

"C:\\windows\\file.txt"
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but Windows (and perl) allow you to use the "/" (forward-slash) instead of backslash, and using "/" does NOT requirie doubling up, and is easier to read.

As you become more familiar with perl, you will understand the reasons to write "open" in the following form:

my $filename="C:\\windows\\file.txt" ; ## or "C:/windows/file.txt" 

open (my $fh, "<", $filename) or die "Could not open $filename: $!";
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This is usually followed by:

while (<$fh>){
  # Process the contents of the record
  # which is stored in $_
}

close $fh or warn "Could not close $filename:$!";
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