my $extract =
  sub {
        my $x = lc($_[0]);
        if ($x =~ s/^(\d+)\s*//) {
            $x = $1 * {
                   mbps => 10**6,
                   kbps => 10**3,
                   bps  => 10**0,
                  }->{$x};
        } else {
            $x = { 't1 line' => 100000 }->{$x};
        }
        die "Bad input $_[0]" unless $x;
        return $x;
      };

my @sorted =
    map  { $_->[0] }
    sort { $a->[1] <=> $b->[1] }
    map  [ $_, $extract->( $_ ) ],
    @array;

##</code><code>##

{    $a->[1] <=> $b->[1]
  or $b->[2] <=> $a->[2]
  or $a->[3] cmp $b->[3]
  # ...compare as many sort keys as you please
}

##</code><code>##

{
  mbps => 10**6,
  kbps => 10**3,
  bps  => 10**0,
},
{ 't1 line' => 100000 }

##</code><code>##

my %lookup = (
  mbps => 10**6,
  kbps => 10**3,
  bps  => 10**0,
  't1 line' => 100000
);

my $extract =
  sub {
        my $x = lc($_[0]);
        if ($x =~ s/^(\d+)\s*//) {
            $x = $1 * $lookup{ $x };
        } else {
            $x = $lookup{ $x };
        }
        die "Bad input $_[0]" unless $x;
        return $x;
      };
# etc.