use strict;
use warnings;
use 5.010;

use English;

{
    #Turn on inplace editing for <> operator, no backup file:
    local $INPLACE_EDIT = "";  
   
    local @ARGV = "./test/data.txt"; 
    #...or list file name on command line

    while(my $line = <>) {
        $line =~ s/hello/goodbye/;   #alter the line
        print $line;  #...then print() it (*required*)
        
    }
}