This is a bit over-generalized, but allows for easy extension.

>perl -wMstrict -le
"use Regexp::Common qw(number);
 ;;
 my %conversion = (
   K => 1_000,
   M => 1_000_000,
   B => 1_000_000_000,
   L => 100_000,  LAKH => 100_000,
   );
 my $suffix =
   qr{ (?i) @{[ join q{|}, reverse sort keys %conversion ]} }xms;
 ;;
 for my $n (qw(28.04B 376.92M 12.3K 98.76Lakh 7l 23.45k), @ARGV) {
   my ($base, $mult) =
     $n =~ m{ \A ($RE{num}{real}) ($suffix) \z }xmsg;
   print qq{'$n' => }, $base * $conversion{uc $mult};
   }
 ;;
 my $s = 'w 28.04b x 376.92M y 98.76L z';
 $s =~ s{ ($RE{num}{real}) ($suffix) }
        { $1 * $conversion{uc $2}    }xmsge;
 print qq{'$s'};
"
'28.04B' => 28040000000
'376.92M' => 376920000
'12.3K' => 12300
'98.76Lakh' => 9876000
'7l' => 700000
'23.45k' => 23450
'w 28040000000 x 376920000 y 9876000 z'
[download]

Update: Added multiple conversions in a string to example.