Ok, you can use a one liner to transform the arguments into key=value pairs in a hash table.

#!/usr/bin/perl -w
use strict;
use Data::Dumper;

my %arg = map{my($key,$val)=split/=/;$key=>$val}@ARGV;

print Dumper(\%arg);
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And when running this with the command-line parameters in your example, I got the following result:

$VAR1 = {
          'lexwhere' => '\'in(\'DIS\', \'DIM\', \'DIR\')\'',
          'title' => '\'this is a title\'',
          'vchtyp' => 'I',
          'jrnltyp' => 'D'
        };
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