#!/usr/bin/perl
use strict;
use warnings;

my $str = "item1 | 0 |  |   item2| item3 
|item4 
 |
 ";

my @cleaned1 = map { clean_no_side_effects($_) } split( /\|/, $str );
my @cleaned2 = grep { clean_no_side_effects($_) } split( /\|/, $str );

print "*"x25, "\n";
print join "\n", @cleaned1;
print "*"x25, "\n";
print join "\n", @cleaned2;
print "*"x25, "\n";

sub clean_no_side_effects {  
    my $string = shift;
    $string =~ s/^\s+|\s+$//g;
    return $string;
}

sub clean_modify {   ## don't use, still using side effects for grep to work
    $_[0] =~ s/^\s+?|\s+?$//g;   # '?' isn't needed here since \s never matches '|'
    return $_[0];
}

sub clean {  ## don't use
    chomp( $_[0] );
    $_[0] =~ s/^\s+//g;
    $_[0] =~ s/\s+$//g;
}
__END__
*************************
item1
0

item2
item3
item4
*************************
item1 
   item2
 item3 

item4 
 *************************