open(DLOG, '<', "D:\\PROJ\\N12${X_info}_X$X_info\\dataInfo_X${Y_info}_
+Y${Z_info}_decode.csv") or die "we have a problem: $!";
#             ^
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Note that I needed to add the comma after the mode, it's not optional.

Also, a backslash is special in double quotes, so it needs to be backslashed to keep its literal meaning.

Moreover, a variable name can't be followed by an underscore (or any other character valid in a variable name) in double quotes, e.g. "$x_" means the variable named $x_, not $x followed by an underscore; you might need to use the curly braces syntax "${x}_".

Even better, use sprintf:

open(DLOG, '<', sprintf 'D:\PROJ\N12%s_X%s\dataInfo_X%s_Y%s_decode.csv
+', $X_info, $X_info, $Y_info, $Z_info) or die "we have a problem: $!"
+;
#                                   ~~  ~~           ~~  ~~
[download]

The usual rant about using lexical filehandles will come shortly.