#!/usr/bin/perl -w
    use strict;
    print "Perl version: $]\n";
    print "UIDs real $<  \t effective $>\n";
    ($>, $<) = ($<, $>);      # swap real uid and effective uid
    print "UIDs real $<  \t effective $>\n";
    ($>, $<) = ($<, $>);      # swap real uid and effective uid
    print "UIDs real $<  \t effective $>\n";
    ($>, $<) = ($<, $>);      # swap real uid and effective uid
    print "UIDs real $<  \t effective $>\n";