#!/usr/bin/perl

use Data::Dumper;

sub get_day_name {
        return "first"  if $_[0] =~ /one/;
        return "second" if $_[0] =~ /two/;
        return "third"  if $_[0] =~ /three/;
        return;
}

print Dumper {map {$_ => get_day_name($_)} <DATA>};

__DATA__
one
two
three

##</code><code>##

$VAR1 = {
          'two
' => 'second',
          'three
' => 'third',
          'one
' => 'first'
        };