That's not going to help. $/ already is "\012" on Windows.

When reading, "\015\012" is converted to "\012" in one of the PerlIO layers, before readline gets a hold of the data, and therefore before $/ is applied.

When writing, "\012" is converted to "\015\012" in one of the PerlIO layers, after print sends off the data, and therefore after $\ is applied. That's why "\n" ("\012") is used instead of "\r\n" ("\015\012") when ending a line.

Maybe binmode is on, in which case the "\015\012" wouldn't be changed to "\012".
Maybe the file is in the old Mac format ("\015").
Maybe the file is in some corrupted format ("\015\015\012", which would look like "\015\012" when $/ is applied).