Effective Perl Programming: Writing Better Programs with Perl

undef operator:

       clearing array variable with;  

       clearing hash variable with  

undef:

       as array element[undef:array]  

       as hash element[undef:hash]  

       in newly created arrays[undef:newly created arrays]  

       instead of empty list[undef:empty list]  

       instead of false[undef:false]  

       verb.   [See undef operator]

underscore pseudo-filehandle:

       in file tests[underscore pseudo-filehandle:file tests];  

unitialized value:

       -w and;  

UNIVERSAL package:

       AUTOLOAD subroutine and  

       package of last resort;   2nd  

unpack operator:

       computing checksums with  

       data munging with;  

       format specifiers  

       processing columns with;  

       repeat counts for specifiers  

        translates binary data into Perl types  

       uudecoding with  

       vs. split[unpack operator:split]  

untainting data  

URI::Escape module  

use directive:

       arguments to  

       autoload path and  

       based on BEGIN and use  

       changing include path in BEGIN block  

       compile-time rather than run-time feature  

       empty list as argument  

       loading module with;  

       on module in build directory[use directive:module in build directory]  

       searches module include path  

       supplanting require  

USENET   2nd   3rd  

uuencoding/decoding:

       with pack and unpack