#!/usr/bin/perl -w
use strict;
use Data::Dumper;

my $h = f(qw[ foo => zoo moo too
              bar => car far
              bar => zar tar
              qux => mux ]);

print Dumper $h;

sub f {
    my( %hash, $y );
    my $key = my $x = shift;
    while($y = shift){
        if( $y eq '=>' ){
            pop( @{$hash{$key}});
            $key= $x;
            $y = shift;
        }
        push( @{$hash{$key}}, $y );
        $x = $y;
    }
    return \%hash;
}