#!/usr/bin/perl -w

$string = '   abc   def   ';

@array1 = split " ", $string;

@array2 = split ?\s+?, $string;

print '2: ' . ( join '|', @array1 ) . "\n";

print '3: ' . ( join '|', @array2 ) . "\n";

##</code><code>##

BEGIN { $^W = 1; }
$string = '   abc   def   ';
@array1 = split(?\s+?, $string, 0);
@array2 = split(?\s+?, $string, 0);
print '2: ' . join('|', @array1) . "\n";
print '3: ' . join('|', @array2) . "\n";

##</code><code>##

2: abc|def
3: |abc|def