As is often the case with Perl, you can cheat. :)

#!/usr/bin/perl -w
use strict;

my $a = "     a: b c: d              e:         f   ";
$a =~ y/://d;
my %h = eval "qw/$a/";   # The Evil String Eval

print "Key [$_] | Value [$h{$_}]\n" for keys %h;
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-- 
Human history becomes more and more a race between education and catastrophe. -- HG Wells