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


##</code><code>##

    while(my $line = $INFILE) 

##</code><code>##

{
    local $^I = "";
    ...
    ...


}

##</code><code>##

~/pperl_programs$ cat data.txt
DEVICE=eth0
ONBOOT=yes
BOOTPROTO=static
TYPE=Ethernet
IPADDR=10.9.0.200
NETMASK=255.255.0.0
GATEWAY=10.9.1.254


~/pperl_programs$ perl 1.pl

~/pperl_programs$ cat data.txt
DEVICE=eth0
ONBOOT=no
BOOTPROTO=static
TYPE=Wifi
IPADDR=10.9.0.200
NETMASK=255.255.0.0
GATEWAY=10.9.1.254