se strict;
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Produces the error message:

Can't locate object method "se" via package "strict" (perhaps you forg
+ot to load "strict"?)
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my $data = `/sbin/ifconfig | grep “RX bytes” | head -1`;
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I guess you are assuming that the "certain device" you want information on is the first device listed by ifconfig?

$data =~ /RX bytes\:(\d+) .*TX bytes\:(\d+) .*/;
my $recv = $1/1024;
my $sent=$2/1024;
$recv =~ s/\..*//;
$sent =~ s/\..*//;
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You shouldn't use the variables $1 and $2 unless the regular expression matched correctly otherwise the values in $1 and $2 will be from the last successful match. Is there any reason that you didn't use the int function instead of the substitution operator?

You probably want something like this:

sub get_measures {
    my $device = qr/\A\Q$_[0]\E\s/;  # pass device name as first argum
+ent

    local $/ = '';  # paragraph mode
    my ( $recv, $sent ) = map {
        /$device/ && /RX bytes\:(\d+) .*?TX bytes\:(\d+)/
            ? int( $1 / 1024 ), int( $2 / 1024 )
            : ()
        } qx[/sbin/ifconfig];

    return $recv, $sent;
    }
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