use feature 'say';
use DateTime::Format::Strptime qw(strptime strftime);
use Time::Piece;


my $raw_date = '2012-01-12';




# Using tr///; built into Perl.
( my $date = $raw_date ) =~ tr/-//d;
say $date;




# From Time::Piece; core since 5.10.
$date = Time::Piece
  ->strptime( $raw_date, "%Y-%m-%d" )
  ->ymd('');
say $date;




# From DateTime::Format::Strptime; imported functions.
$date = strftime( "%Y%m%d", strptime( "%Y-%m-%d", $raw_date ) );
say $date;




# From DateTime::Format::Strptime; OO interface.
$date = DateTime::Format::Strptime
  ->new( pattern => "%Y-%m-%d" )
  ->parse_datetime($raw_date)
  ->ymd('');
say $date;