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


my @month_name =
  qw/ january february march april may june july august september /;

my $month = {}; 
for ( 0 .. $#month_name ) { 
    $month_name[$_] =~ s/(\w{3})(\w*)/$1(?:$2)?/;
    $month->{qr/$month_name[$_]/} = $_ + 1;

}

sub month_to_num {
    my $date = shift;
    for ( keys %$month ) { 
        last if $date =~ s/$_/$month->{$_}/;
    }   
    return $date;
}

printf "%02s %02d %4d\n", split /\s+/, month_to_num($_)
  for (
    'dec 7 2008',
    'may 25 2003',
    'march 01 1897'
  );  

# Output: 
# dec 07 2008
# 05 25 2003
# 03 01 1897
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hth,
PooLpi