# strategy 1

my $var;

# other stuff

sub mysub {
    # do stuff -- don't declare my $var here, though.  It will mask the one you want to set.
    $var = "whatever"; # sets $var declared above to "whatever"
    
}

##</code><code>##

# option 2

my $var = mysub();

sub mysub {
     # do stuff
     $var = "whatever";
     return $var; # return is optional here, but makes what's going on explicit.
}

##</code><code>##

perl -e 'print "How sweet does a rose smell? "; chomp ($n = <STDIN>); $rose = "smells sweet to degree $n"; *other_name = *rose; print "$other_name\n"'