You're opening a file twice, that may not be necessary if you reconstruct your code to use the eof function to detect the end of the file, there is a difference between eof and eof() however and the later will only detect the end of the last file in a list of files provided whereas eof -without the parentheses- can detect the end of each file ...

use strict;
use warnings;

while(<DATA>){
        if(eof){  #Check if the last line has ' last ' 
                print ~/\slast\s/ ? 'yes' : 'no';
                }
        }

__DATA__
one line
two lines
three lines
this is the last one
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