#!/usr/bin/perl
use strict;
use warnings;

foreach my $y (qw(19.990 19.9 19. 19.559 19.00 19.34776454540000))
{
   my $x =$y."00"; # at least 2 digits past the decimal
   $x =~ s/(\d+)(\.)(\d{2})(\d+)?/$1$3/;
   print "result: $y => $x\n";
}
__END__

result: 19.990 => 1999
result: 19.9 => 1990
result: 19. => 1900
result: 19.559 => 1955
result: 19.00 => 1900
result: 19.34776454540000 => 1934