return $inp or "";
[download]

Because of the low precedence of the or operator that will not do what you seem to think it will:

$ perl -le'
sub prompt {
    my $inp = shift;
    return $inp or "zzz";
    }
print prompt( $_ ) for undef, 0, 1, 2;
'

0
1
2
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You need to use the higher precedence || operator:

$ perl -le'
sub prompt {
    my $inp = shift;
    return $inp || "zzz";
    }
print prompt( $_ ) for undef, 0, 1, 2;
'
zzz
zzz
1
2
[download]

---

while ( chomp(my $inpt = <STDIN>) != 0  ) {
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That is usually written as:

while ( my $inpt = <STDIN>  ) {
    chomp $inpt;
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---

            system("ifconfig wlan0 up") if ( (my $ifconf = `ifconfig`)
+ !~ /wlan0/ );
[download]

You never use the $ifconf variable anywhere else in your program so why are you creating it?    Just do:

            system 'ifconfig wlan0 up' if `ifconfig` !~ /wlan0/;
[download]