use strict;
use warnings; 
use 5.020;

my %new_values = (
    ONBOOT  => 'no',
    TYPE    => 'Wifi',
);

my $file_name = "data.txt";
read_file($file_name, \%new_values);


sub read_file {
    my ($fname, $new_values_href) = @_;

    local $^I = ".bak";  #Enable inplace editing for this block only.
    local @ARGV = $fname; #Set value for @ARGV for this block only.

    while (my $line = <>) {
        my ($name, $val) = split /=/, $line;
        my $replacement_value = $new_values_href->{$name};

        if (defined $replacement_value) {
            say "$name=$replacement_value"; #Output goes to file 
        }
        else {
            print $line;  #Output goes to file
        }
    }
} #Restore $^I and @ARGV to the values they had before the block