#!/usr/bin/perl -l

use strict;
use warnings;

my %foo = (
    _foo => 'FOO',
    _bar => 'BAR',
    _baz => 'BAZ',
    zum  => 'ZUM',     # do not make this one a "real" variable
);  

{   # limit the scope of the following 'no strict' 
    no strict 'refs';

    # There be magic here!  This will get the keys from %foo
    # then attempt to remove the leading '_'.  If it works, 
    # the *modified* key gets passed along; otherwise, the
    # key is stripped from your processing list.  We then
    # dynamically create a variable with the name of the
    # modified key and assign it the value of the unmodified
    # key in the hash.
    $$_ = $foo{"_$_"} for (grep { s/^_(.*)/$1/ } keys %foo);
}   

# this is so we can speak the variable's name without Perl throwing a fit
no strict 'vars';
print for ($foo, $bar, $baz, $zum);  # should produce one 'unitialized' warning