Something along the lines of 
my $line = ";field;;field;\t;field; ;field;field";
my @line = split ";", $line;
my @null = grep { defined $_ } map { $line[$_] =~ /^$/ ? $_ : undef } 
+(0..$#line);

print "line contains ", scalar @null, " null fields at offset(s): @nul
+l";
#line contains 2 null fields at offset(s): 0 2

[download]

?

Update: To fit in the OP's specified requirements:

use strict;

while ( <DATA> )
{
    my @line = split /\|/, $_;
    my @null = grep { defined $_ } map { $line[$_] =~ /^$/ ? $_ : unde
+f } (0..$#line);
    print "line contains ", scalar @null, " null fields at offset(s): 
+@null\n";
}

#line contains 3 null fields at offset(s): 1 3 4
#line contains 2 null fields at offset(s): 2 4
#line contains 3 null fields at offset(s): 0 1 4
#line contains 2 null fields at offset(s): 1 2 4

__DATA__
first||third||
alpha|beta||delta|
||c|d|
one|||four|

[download]


holli, /regexed monk/

In reply to Re: identifying null fields in bar delimited records by holli
in thread identifying null fields in bar delimited records by jjohhn

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