#!/usr/bin/perl -w
use strict;

my @tests = ('50 ma', '10ma', '2.3', '-.2 ma', '3.', 
             '4.0', '10ba');

foreach my $input (@tests)
{
   my ($amps, $flag_ma)= $input=~ /^\s*([-+]?\d*\.?\d+)\s*(ma|mA)?\s*$/;
  
   $amps /=1000    if defined $flag_ma;
   
   if (defined $amps)  
   {
       print "$amps amps\n";
   }
   else
   {
       print "$input is an illegal entry\n";
   }
}

__END__

0.05 amps
0.01 amps
2.3 amps
-0.0002 amps
3. is an illegal entry
4.0 amps
10ba is an illegal entry