One More Way to Do It: grep: 

>perl -wMstrict -le
"my ($foo, $bar);
 my ($no_ws, $some_ws, $lotsa_ws) =
   ('no_ws', ' some_ws ', '  lotsa  ws  ');
 printf qq{'$_'  } for $no_ws, $some_ws, $lotsa_ws;
 print '';
 ;;
 s{ \A \s+ | \s+ \z }''xmsg
   for grep defined, $no_ws, $foo, $some_ws, $bar, $lotsa_ws;
 printf qq{'$_'  } for $no_ws, $some_ws, $lotsa_ws;
"
'no_ws'  ' some_ws '  '  lotsa  ws  '
'no_ws'  'some_ws'  'lotsa  ws'

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Update: However,  grep as used above has the disadvantage of creating an output list that may be the same size as the input list; Perl then has twice as much data to deal with.

The advantage of a looping statement like
    defined and s/^\s+|\s+$//g for LIST;
is that the elements of  LIST are operated on in place and no new list is created.

In reply to Re: Test if multiple variables are defined by AnomalousMonk
in thread Test if multiple variables are defined by stroke

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